Computer Security Incident Handling Guide A.8 NIST 800 61r2 (2012)

A.8_NIST%20800-61r2%20Computer%20Security%20Incident%20Handling%20Guide%20(2012)

NIST.SP.800-61r2%20Incident%20Handling%20Guide

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Computer Security

Incident Handling Guide

Recommendations of the National Institute

of Standards and Technology

Paul Cichonski

Tom Millar

Tim Grance

Karen Scarfone

Special Publication 800-61

Revision 2

http://dx.doi.org/10.6028/NIST.SP.800-61r2

NIST Special Publication 800-61

Revision 2

Computer Security Incident Handling

Guide

Recommendations of the National

Institute of Standards and Technology

Paul Cichonski

Computer Security Division

Information Technology Laboratory

National Institute of Standards and Technology

Gaithersburg, MD

Tom Millar

United States Computer Emergency Readiness Team

National Cyber Security Division

Department of Homeland Security

Tim Grance

Computer Security Division

Information Technology Laboratory

National Institute of Standards and Technology

Gaithersburg, MD

Karen Scarfone

Scarfone Cybersecurity

C O M P U T E R S E C U R I T Y

August 2012

U.S. Department of Commerce

Rebecca Blank, Acting Secretary

National Institute of Standards and Technology

Patrick D. Gallagher,

Under Secretary of Commerce for Standards and Technology

and Director

http://dx.doi.org/10.6028/NIST.SP.800-61r2

COMPUTER SECURITY INCIDENT HANDLING GUIDE

Reports on Computer Systems Technology

The Information Technology Laboratory (ITL) at the National Institute of Standards and Technology

(NIST) promotes the U.S. economy and public welfare by providing technical leadership for the Nation’s

measurement and standards infrastructure. ITL develops tests, test methods, reference data, proof of

concept implementations, and technical analyses to advance the development and productive use of

information technology. ITL’s responsibilities include the development of management, administrative,

technical, and physical standards and guidelines for the cost-effective security and privacy of other than

national security-related information in Federal information systems. The Special Publication 800-series

reports on ITL’s research, guidelines, and outreach efforts in information system security, and its

collaborative activities with industry, government, and academic organizations.

COMPUTER SECURITY INCIDENT HANDLING GUIDE

iii

Authority

This publication has been developed by NIST to further its statutory responsibilities under the Federal

Information Security Management Act (FISMA), Public Law (P.L.) 107-347. NIST is responsible for

developing information security standards and guidelines, including minimum requirements for Federal

information systems, but such standards and guidelines shall not apply to national security systems

without the express approval of appropriate Federal officials exercising policy authority over such

systems. This guideline is consistent with the requirements of the Office of Management and Budget

(OMB) Circular A-130, Section 8b(3), Securing Agency Information Systems, as analyzed in Circular A-

130, Appendix IV: Analysis of Key Sections. Supplemental information is provided in Circular A-130,

Appendix III, Security of Federal Automated Information Resources.

Nothing in this publication should be taken to contradict the standards and guidelines made mandatory

and binding on Federal agencies by the Secretary of Commerce under statutory authority. Nor should

these guidelines be interpreted as altering or superseding the existing authorities of the Secretary of

Commerce, Director of the OMB, or any other Federal official. This publication may be used by

nongovernmental organizations on a voluntary basis and is not subject to copyright in the United States.

Attribution would, however, be appreciated by NIST.

National Institute of Standards and Technology Special Publication 800-61 Revision 2

Natl. Inst. Stand. Technol. Spec. Publ. 800-61 Revision 2, 79 pages (Aug. 2012)

CODEN: NSPUE2

Comments on this publication may be submitted to:

National Institute of Standards and Technology

Attn: Computer Security Division, Information Technology Laboratory

100 Bureau Drive (Mail Stop 8930), Gaithersburg, MD 20899-8930

Certain commercial entities, equipment, or materials may be identified in this document in order to describe an

experimental procedure or concept adequately. Such identification is not intended to imply recommendation or

endorsement by NIST, nor is it intended to imply that the entities, materials, or equipment are necessarily the

best available for the purpose.

There may be references in this publication to other publications currently under development by NIST in

accordance with its assigned statutory responsibilities. The information in this publication, including concepts

and methodologies, may be used by Federal agencies even before the completion of such companion

publications. Thus, until each publication is completed, current requirements, guidelines, and procedures, where

they exist, remain operative. For planning and transition purposes, Federal agencies may wish to closely follow

the development of these new publications by NIST.

Organizations are encouraged to review all draft publications during public comment periods and provide

feedback to NIST. All NIST publications, other than the ones noted above, are available at

http://csrc.nist.gov/publications.

http://dx.doi.org/10.6028/NIST.SP.800-61r2

COMPUTER SECURITY INCIDENT HANDLING GUIDE

Abstract

Computer security incident response has become an important component of information technology (IT)

programs. Because performing incident response effectively is a complex undertaking, establishing a

successful incident response capability requires substantial planning and resources. This publication

assists organizations in establishing computer security incident response capabilities and handling

incidents efficiently and effectively. This publication provides guidelines for incident handling,

particularly for analyzing incident-related data and determining the appropriate response to each incident.

The guidelines can be followed independently of particular hardware platforms, operating systems,

protocols, or applications.

Keywords

computer security incident; incident handling; incident response; information security

COMPUTER SECURITY INCIDENT HANDLING GUIDE

Acknowledgments

The authors, Paul Cichonski of the National Institute of Standards and Technology (NIST), Tom Millar of

the United States Computer Emergency Readiness Team (US-CERT), Tim Grance of NIST, and Karen

Scarfone of Scarfone Cybersecurity wish to thank their colleagues who reviewed drafts of this document

and contributed to its technical content, including John Banghart of NIST; Brian Allen, Mark Austin,

Brian DeWyngaert, Andrew Fuller, Chris Hallenbeck, Sharon Kim, Mischel Kwon, Lee Rock, Richard

Struse, and Randy Vickers of US-CERT; and Marcos Osorno of the Johns Hopkins University Applied

Physics Laboratory. A special acknowledgment goes to Brent Logan of US-CERT for his graphics

assistance. The authors would also like to thank security experts Simon Burson, Anton Chuvakin

(Gartner), Fred Cohen (Fred Cohen & Associates), Mariano M. del Rio (SIClabs), Jake Evans (Tripwire),

Walter Houser (SRA), Panos Kampanakis (Cisco), Kathleen Moriarty (EMC), David Schwalenberg

(National Security Agency), and Wes Young (Research and Education Networking Information Sharing

and Analysis Center [REN-ISAC]), as well as representatives of the Blue Glacier Management Group, the

Centers for Disease Control and Prevention, the Department of Energy, the Department of State, and the

Federal Aviation Administration for their particularly valuable comments and suggestions.

The authors would also like to acknowledge the individuals that contributed to the previous versions of

the publication. A special thanks goes to Brian Kim of Booz Allen Hamilton, who co-authored the

original version; to Kelly Masone of Blue Glacier Management Group, who co-authored the first revision;

and also to Rick Ayers, Chad Bloomquist, Vincent Hu, Peter Mell, Scott Rose, Murugiah Souppaya, Gary

Stoneburner, and John Wack of NIST; Don Benack and Mike Witt of US-CERT; and Debra Banning,

Pete Coleman, Alexis Feringa, Tracee Glass, Kevin Kuhlkin, Bryan Laird, Chris Manteuffel, Ron

Ritchey, and Marc Stevens of Booz Allen Hamilton for their keen and insightful assistance throughout the

development of the document, as well as Ron Banerjee and Gene Schultz for their work on a preliminary

draft of the document. The authors would also like to express their thanks to security experts Tom Baxter

(NASA), Mark Bruhn (Indiana University), Brian Carrier (CERIAS, Purdue University), Eoghan Casey,

Johnny Davis, Jr. (Department of Veterans Affairs), Jim Duncan (BB&T), Dean Farrington (Wells Fargo

Bank), John Hale (University of Tulsa), Georgia Killcrece (CERT®/CC), Barbara Laswell (CERT®/CC),

Pascal Meunier (CERIAS, Purdue University), Jeff Murphy (University of Buffalo), Todd O’Boyle

(MITRE), Marc Rogers (CERIAS, Purdue University), Steve Romig (Ohio State University), Robin

Ruefle (CERT®/CC), Gene Schultz (Lawrence Berkeley National Laboratory), Michael Smith (US-

CERT), Holt Sorenson, Eugene Spafford (CERIAS, Purdue University), Ken van Wyk, and Mark Zajicek

(CERT®/CC), as well as representatives of the Department of the Treasury, for their particularly valuable

comments and suggestions.

COMPUTER SECURITY INCIDENT HANDLING GUIDE

Table of Contents

Executive Summary ................................................................................................................. 1

1. Introduction ...................................................................................................................... 4

1.1 Authority .................................................................................................................... 4

1.2 Purpose and Scope ................................................................................................... 4

1.3 Audience ................................................................................................................... 4

1.4 Document Structure .................................................................................................. 4

2. Organizing a Computer Security Incident Response Capability ................................... 6

2.1 Events and Incidents ................................................................................................. 6

2.2 Need for Incident Response ...................................................................................... 6

2.3 Incident Response Policy, Plan, and Procedure Creation .......................................... 7

2.3.1 Policy Elements............................................................................................. 7

2.3.2 Plan Elements ............................................................................................... 8

2.3.3 Procedure Elements ...................................................................................... 8

2.3.4 Sharing Information With Outside Parties ...................................................... 9

2.4 Incident Response Team Structure ......................................................................... 13

2.4.1 Team Models ...............................................................................................13

2.4.2 Team Model Selection..................................................................................14

2.4.3 Incident Response Personnel .......................................................................16

2.4.4 Dependencies within Organizations .............................................................17

2.5 Incident Response Team Services .......................................................................... 18

2.6 Recommendations .................................................................................................. 19

3. Handling an Incident .......................................................................................................21

3.1 Preparation .............................................................................................................. 21

3.1.1 Preparing to Handle Incidents ......................................................................21

3.1.2 Preventing Incidents .....................................................................................23

3.2 Detection and Analysis ............................................................................................ 25

3.2.1 Attack Vectors ..............................................................................................25

3.2.2 Signs of an Incident ......................................................................................26

3.2.3 Sources of Precursors and Indicators ...........................................................27

3.2.4 Incident Analysis ..........................................................................................28

3.2.5 Incident Documentation ................................................................................30

3.2.6 Incident Prioritization ....................................................................................32

3.2.7 Incident Notification ......................................................................................33

3.3 Containment, Eradication, and Recovery................................................................. 35

3.3.1 Choosing a Containment Strategy ................................................................35

3.3.2 Evidence Gathering and Handling ................................................................36

3.3.3 Identifying the Attacking Hosts .....................................................................37

3.3.4 Eradication and Recovery ............................................................................37

3.4 Post-Incident Activity ............................................................................................... 38

3.4.1 Lessons Learned ..........................................................................................38

3.4.2 Using Collected Incident Data ......................................................................39

3.4.3 Evidence Retention ......................................................................................41

3.5 Incident Handling Checklist ..................................................................................... 42

3.6 Recommendations .................................................................................................. 42

4. Coordination and Information Sharing ..........................................................................45

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vii

4.1 Coordination ............................................................................................................ 45

4.1.1 Coordination Relationships ..........................................................................46

4.1.2 Sharing Agreements and Reporting Requirements ......................................47

4.2 Information Sharing Techniques .............................................................................. 48

4.2.1 Ad Hoc .........................................................................................................48

4.2.2 Partially Automated ......................................................................................48

4.2.3 Security Considerations ...............................................................................49

4.3 Granular Information Sharing .................................................................................. 49

4.3.1 Business Impact Information ........................................................................49

4.3.2 Technical Information ...................................................................................50

4.4 Recommendations .................................................................................................. 51

List of Appendices

Appendix A— Incident Handling Scenarios ..........................................................................52

A.1 Scenario Questions ................................................................................................. 52

A.2 Scenarios ................................................................................................................ 53

Appendix B— Incident-Related Data Elements .....................................................................58

B.1 Basic Data Elements ............................................................................................... 58

B.2 Incident Handler Data Elements .............................................................................. 59

Appendix C— Glossary ..........................................................................................................60

Appendix D— Acronyms ........................................................................................................61

Appendix E— Resources........................................................................................................63

Appendix F— Frequently Asked Questions ..........................................................................65

Appendix G— Crisis Handling Steps .....................................................................................68

Appendix H— Change Log .....................................................................................................69

List of Figures

Figure 2-1. Communications with Outside Parties .....................................................................10

Figure 3-1. Incident Response Life Cycle ..................................................................................21

Figure 3-2. Incident Response Life Cycle (Detection and Analysis) ...........................................25

Figure 3-3. Incident Response Life Cycle (Containment, Eradication, and Recovery) ...............35

Figure 3-4. Incident Response Life Cycle (Post-Incident Activity) ..............................................38

Figure 4-1. Incident Response Coordination .............................................................................46

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List of Tables

Table 3-1. Common Sources of Precursors and Indicators .......................................................27

Table 3-2. Functional Impact Categories ...................................................................................33

Table 3-3. Information Impact Categories .................................................................................33

Table 3-4. Recoverability Effort Categories ...............................................................................33

Table 3-5. Incident Handling Checklist ......................................................................................42

Table 4-1. Coordination Relationships ......................................................................................47

COMPUTER SECURITY INCIDENT HANDLING GUIDE

Executive Summary

Computer security incident response has become an important component of information technology (IT)

programs. Cybersecurity-related attacks have become not only more numerous and diverse but also more

damaging and disruptive. New types of security-related incidents emerge frequently. Preventive activities

based on the results of risk assessments can lower the number of incidents, but not all incidents can be

prevented. An incident response capability is therefore necessary for rapidly detecting incidents,

minimizing loss and destruction, mitigating the weaknesses that were exploited, and restoring IT services.

To that end, this publication provides guidelines for incident handling, particularly for analyzing incident-

related data and determining the appropriate response to each incident. The guidelines can be followed

independently of particular hardware platforms, operating systems, protocols, or applications.

Because performing incident response effectively is a complex undertaking, establishing a successful

incident response capability requires substantial planning and resources. Continually monitoring for

attacks is essential. Establishing clear procedures for prioritizing the handling of incidents is critical, as is

implementing effective methods of collecting, analyzing, and reporting data. It is also vital to build

relationships and establish suitable means of communication with other internal groups (e.g., human

resources, legal) and with external groups (e.g., other incident response teams, law enforcement).

This publication assists organizations in establishing computer security incident response capabilities and

handling incidents efficiently and effectively. This revision of the publication, Revision 2, updates

material throughout the publication to reflect the changes in attacks and incidents. Understanding threats

and identifying modern attacks in their early stages is key to preventing subsequent compromises, and

proactively sharing information among organizations regarding the signs of these attacks is an

increasingly effective way to identify them.

Implementing the following requirements and recommendations should facilitate efficient and effective

incident response for Federal departments and agencies.

Organizations must create, provision, and operate a formal incident response capability. Federal

law requires Federal agencies to report incidents to the United States Computer Emergency

Readiness Team (US-CERT) office within the Department of Homeland Security (DHS).

The Federal Information Security Management Act (FISMA) requires Federal agencies to establish

incident response capabilities. Each Federal civilian agency must designate a primary and secondary point

of contact (POC) with US-CERT and report all incidents consistent with the agency’s incident response

policy. Each agency is responsible for determining how to fulfill these requirements.

Establishing an incident response capability should include the following actions:

 Creating an incident response policy and plan

 Developing procedures for performing incident handling and reporting

 Setting guidelines for communicating with outside parties regarding incidents

 Selecting a team structure and staffing model

 Establishing relationships and lines of communication between the incident response team and other

groups, both internal (e.g., legal department) and external (e.g., law enforcement agencies)

 Determining what services the incident response team should provide

COMPUTER SECURITY INCIDENT HANDLING GUIDE

 Staffing and training the incident response team.

Organizations should reduce the frequency of incidents by effectively securing networks, systems,

and applications.

Preventing problems is often less costly and more effective than reacting to them after they occur. Thus,

incident prevention is an important complement to an incident response capability. If security controls are

insufficient, high volumes of incidents may occur. This could overwhelm the resources and capacity for

response, which would result in delayed or incomplete recovery and possibly more extensive damage and

longer periods of service and data unavailability. Incident handling can be performed more effectively if

organizations complement their incident response capability with adequate resources to actively maintain

the security of networks, systems, and applications. This includes training IT staff on complying with the

organization’s security standards and making users aware of policies and procedures regarding

appropriate use of networks, systems, and applications.

Organizations should document their guidelines for interactions with other organizations regarding

incidents.

During incident handling, the organization will need to communicate with outside parties, such as other

incident response teams, law enforcement, the media, vendors, and victim organizations. Because these

communications often need to occur quickly, organizations should predetermine communication

guidelines so that only the appropriate information is shared with the right parties.

Organizations should be generally prepared to handle any incident but should focus on being

prepared to handle incidents that use common attack vectors.

Incidents can occur in countless ways, so it is infeasible to develop step-by-step instructions for handling

every incident. This publication defines several types of incidents, based on common attack vectors; these

categories are not intended to provide definitive classification for incidents, but rather to be used as a

basis for defining more specific handling procedures. Different types of incidents merit different response

strategies. The attack vectors are:

 External/Removable Media: An attack executed from removable media (e.g., flash drive, CD) or a

peripheral device.

 Attrition: An attack that employs brute force methods to compromise, degrade, or destroy systems,

networks, or services.

 Web: An attack executed from a website or web-based application.

 Email: An attack executed via an email message or attachment.

 Improper Usage: Any incident resulting from violation of an organization’s acceptable usage

policies by an authorized user, excluding the above categories.

 Loss or Theft of Equipment: The loss or theft of a computing device or media used by the

organization, such as a laptop or smartphone.

 Other: An attack that does not fit into any of the other categories.

COMPUTER SECURITY INCIDENT HANDLING GUIDE

Organizations should emphasize the importance of incident detection and analysis throughout the

organization.

In an organization, millions of possible signs of incidents may occur each day, recorded mainly by

logging and computer security software. Automation is needed to perform an initial analysis of the data

and select events of interest for human review. Event correlation software can be of great value in

automating the analysis process. However, the effectiveness of the process depends on the quality of the

data that goes into it. Organizations should establish logging standards and procedures to ensure that

adequate information is collected by logs and security software and that the data is reviewed regularly.

Organizations should create written guidelines for prioritizing incidents.

Prioritizing the handling of individual incidents is a critical decision point in the incident response

process. Effective information sharing can help an organization identify situations that are of greater

severity and demand immediate attention. Incidents should be prioritized based on the relevant factors,

such as the functional impact of the incident (e.g., current and likely future negative impact to business

functions), the information impact of the incident (e.g., effect on the confidentiality, integrity, and

availability of the organization’s information), and the recoverability from the incident (e.g., the time and

types of resources that must be spent on recovering from the incident).

Organizations should use the lessons learned process to gain value from incidents.

After a major incident has been handled, the organization should hold a lessons learned meeting to review

the effectiveness of the incident handling process and identify necessary improvements to existing

security controls and practices. Lessons learned meetings can also be held periodically for lesser incidents

as time and resources permit. The information accumulated from all lessons learned meetings should be

used to identify and correct systemic weaknesses and deficiencies in policies and procedures. Follow-up

reports generated for each resolved incident can be important not only for evidentiary purposes but also

for reference in handling future incidents and in training new team members.

COMPUTER SECURITY INCIDENT HANDLING GUIDE

1. Introduction

1.1 Authority

The National Institute of Standards and Technology (NIST) developed this document in furtherance of its

statutory responsibilities under the Federal Information Security Management Act (FISMA) of 2002,

Public Law 107-347.

NIST is responsible for developing standards and guidelines, including minimum requirements, for

providing adequate information security for all agency operations and assets, but such standards and

guidelines shall not apply to national security systems. This guideline is consistent with the requirements

of the Office of Management and Budget (OMB) Circular A-130, Section 8b(3), “Securing Agency

Information Systems,” as analyzed in A-130, Appendix IV: Analysis of Key Sections. Supplemental

information is provided in A-130, Appendix III.

This guideline has been prepared for use by Federal agencies. It may be used by nongovernmental

organizations on a voluntary basis and is not subject to copyright, though attribution is desired.

Nothing in this document should be taken to contradict standards and guidelines made mandatory and

binding on Federal agencies by the Secretary of Commerce under statutory authority, nor should these

guidelines be interpreted as altering or superseding the existing authorities of the Secretary of Commerce,

Director of the OMB, or any other Federal official.

1.2 Purpose and Scope

This publication seeks to assist organizations in mitigating the risks from computer security incidents by

providing practical guidelines on responding to incidents effectively and efficiently. It includes guidelines

on establishing an effective incident response program, but the primary focus of the document is

detecting, analyzing, prioritizing, and handling incidents. Organizations are encouraged to tailor the

recommended guidelines and solutions to meet their specific security and mission requirements.

1.3 Audience

This document has been created for computer security incident response teams (CSIRTs), system and

network administrators, security staff, technical support staff, chief information security officers (CISOs),

chief information officers (CIOs), computer security program managers, and others who are responsible

for preparing for, or responding to, security incidents.

1.4 Document Structure

The remainder of this document is organized into the following sections and appendices:

 Section 2 discusses the need for incident response, outlines possible incident response team

structures, and highlights other groups within an organization that may participate in incident

handling.

 Section 3 reviews the basic incident handling steps and provides advice for performing incident

handling more effectively, particularly incident detection and analysis.

 Section 4 examines the need for incident response coordination and information sharing.

COMPUTER SECURITY INCIDENT HANDLING GUIDE

 Appendix A contains incident response scenarios and questions for use in incident response tabletop

discussions.

 Appendix B provides lists of suggested data fields to collect for each incident.

 Appendices C and D contain a glossary and acronym list, respectively.

 Appendix E identifies resources that may be useful in planning and performing incident response.

 Appendix F covers frequently asked questions about incident response.

 Appendix G lists the major steps to follow when handling a computer security incident-related crisis.

 Appendix H contains a change log listing significant changes since the previous revision.

COMPUTER SECURITY INCIDENT HANDLING GUIDE

2. Organizing a Computer Security Incident Response Capability

Organizing an effective computer security incident response capability (CSIRC) involves several major

decisions and actions. One of the first considerations should be to create an organization-specific

definition of the term “incident” so that the scope of the term is clear. The organization should decide

what services the incident response team should provide, consider which team structures and models can

provide those services, and select and implement one or more incident response teams. Incident response

plan, policy, and procedure creation is an important part of establishing a team, so that incident response

is performed effectively, efficiently, and consistently, and so that the team is empowered to do what needs

to be done. The plan, policies, and procedures should reflect the team’s interactions with other teams

within the organization as well as with outside parties, such as law enforcement, the media, and other

incident response organizations. This section provides not only guidelines that should be helpful to

organizations that are establishing incident response capabilities, but also advice on maintaining and

enhancing existing capabilities.

2.1 Events and Incidents

An event is any observable occurrence in a system or network. Events include a user connecting to a file

share, a server receiving a request for a web page, a user sending email, and a firewall blocking a

connection attempt. Adverse events are events with a negative consequence, such as system crashes,

packet floods, unauthorized use of system privileges, unauthorized access to sensitive data, and execution

of malware that destroys data. This guide addresses only adverse events that are computer security-

related, not those caused by natural disasters, power failures, etc.

A computer security incident is a violation or imminent threat of violation

of computer security policies,

acceptable use policies, or standard security practices. Examples of incidents

are:

 An attacker commands a botnet to send high volumes of connection requests to a web server, causing

it to crash.

 Users are tricked into opening a “quarterly report” sent via email that is actually malware; running the

tool has infected their computers and established connections with an external host.

 An attacker obtains sensitive data and threatens that the details will be released publicly if the

organization does not pay a designated sum of money.

 A user provides or exposes sensitive information to others through peer-to-peer file sharing services.

2.2 Need for Incident Response

Attacks frequently compromise personal and business data, and it is critical to respond quickly and

effectively when security breaches occur. The concept of computer security incident response has become

widely accepted and implemented. One of the benefits of having an incident response capability is that it

supports responding to incidents systematically (i.e., following a consistent incident handling

methodology) so that the appropriate actions are taken. Incident response helps personnel to minimize

loss or theft of information and disruption of services caused by incidents. Another benefit of incident

response is the ability to use information gained during incident handling to better prepare for handling

An “imminent threat of violation” refers to a situation in which the organization has a factual basis for believing that a

specific incident is about to occur. For example, the antivirus software maintainers may receive a bulletin from the software

vendor, warning them of new malware that is rapidly spreading across the Internet.

For the remainder of this document, the terms “incident” and “computer security incident” are interchangeable.

COMPUTER SECURITY INCIDENT HANDLING GUIDE

future incidents and to provide stronger protection for systems and data. An incident response capability

also helps with dealing properly with legal issues that may arise during incidents.

Besides the business reasons to establish an incident response capability, Federal departments and

agencies must comply with law, regulations, and policy directing a coordinated, effective defense against

information security threats. Chief among these are the following:

 OMB’s Circular No. A-130, Appendix III,

released in 2000, which directs Federal agencies to

“ensure that there is a capability to provide help to users when a security incident occurs in the system

and to share information concerning common vulnerabilities and threats. This capability shall share

information with other organizations … and should assist the agency in pursuing appropriate legal

action, consistent with Department of Justice guidance.”

 FISMA (from 2002),

which requires agencies to have “procedures for detecting, reporting, and

responding to security incidents” and establishes a centralized Federal information security incident

center, in part to:

– “Provide timely technical assistance to operators of agency information systems … including

guidance on detecting and handling information security incidents …

– Compile and analyze information about incidents that threaten information security …

– Inform operators of agency information systems about current and potential information security

threats, and vulnerabilities … .”

 Federal Information Processing Standards (FIPS) 200, Minimum Security Requirements for Federal

Information and Information Systems

, March 2006, which specifies minimum security requirements

for Federal information and information systems, including incident response. The specific

requirements are defined in NIST Special Publication (SP) 800-53, Recommended Security Controls

for Federal Information Systems and Organizations.

 OMB Memorandum M-07-16, Safeguarding Against and Responding to the Breach of Personally

Identifiable Information

, May 2007, which provides guidance on reporting security incidents that

involve PII.

2.3 Incident Response Policy, Plan, and Procedure Creation

This section discusses policies, plans, and procedures related to incident response, with an emphasis on

interactions with outside parties.

2.3.1 Policy Elements

Policy governing incident response is highly individualized to the organization. However, most policies

include the same key elements:

 Statement of management commitment

 Purpose and objectives of the policy

http://www.whitehouse.gov/omb/circulars/a130/a130trans4.html

http://csrc.nist.gov/drivers/documents/FISMA-final.pdf

http://csrc.nist.gov/publications/PubsFIPS.html

http://www.whitehouse.gov/omb/memoranda/fy2007/m07-16.pdf

COMPUTER SECURITY INCIDENT HANDLING GUIDE

 Scope of the policy (to whom and what it applies and under what circumstances)

 Definition of computer security incidents and related terms

 Organizational structure and definition of roles, responsibilities, and levels of authority; should

include the authority of the incident response team to confiscate or disconnect equipment and to

monitor suspicious activity, the requirements for reporting certain types of incidents, the requirements

and guidelines for external communications and information sharing (e.g., what can be shared with

whom, when, and over what channels), and the handoff and escalation points in the incident

management process

 Prioritization or severity ratings of incidents

 Performance measures (as discussed in Section 3.4.2)

 Reporting and contact forms.

2.3.2 Plan Elements

Organizations should have a formal, focused, and coordinated approach to responding to incidents,

including an incident response plan that provides the roadmap for implementing the incident response

capability. Each organization needs a plan that meets its unique requirements, which relates to the

organization’s mission, size, structure, and functions. The plan should lay out the necessary resources and

management support. The incident response plan should include the following elements:

 Mission

 Strategies and goals

 Senior management approval

 Organizational approach to incident response

 How the incident response team will communicate with the rest of the organization and with other

organizations

 Metrics for measuring the incident response capability and its effectiveness

 Roadmap for maturing the incident response capability

 How the program fits into the overall organization.

The organization’s mission, strategies, and goals for incident response should help in determining the

structure of its incident response capability. The incident response program structure should also be

discussed within the plan. Section 2.4.1 discusses the types of structures.

Once an organization develops a plan and gains management approval, the organization should

implement the plan and review it at least annually to ensure the organization is following the roadmap for

maturing the capability and fulfilling their goals for incident response.

2.3.3 Procedure Elements

Procedures should be based on the incident response policy and plan. Standard operating procedures

(SOPs) are a delineation of the specific technical processes, techniques, checklists, and forms used by the

incident response team. SOPs should be reasonably comprehensive and detailed to ensure that the

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priorities of the organization are reflected in response operations. In addition, following standardized

responses should minimize errors, particularly those that might be caused by stressful incident handling

situations. SOPs should be tested to validate their accuracy and usefulness, then distributed to all team

members. Training should be provided for SOP users; the SOP documents can be used as an instructional

tool. Suggested SOP elements are presented throughout Section 3.

2.3.4 Sharing Information With Outside Parties

Organizations often need to communicate with outside parties regarding an incident, and they should do

so whenever appropriate, such as contacting law enforcement, fielding media inquiries, and seeking

external expertise. Another example is discussing incidents with other involved parties, such as Internet

service providers (ISPs), the vendor of vulnerable software, or other incident response teams.

Organizations may also proactively share relevant incident indicator information with peers to improve

detection and analysis of incidents. The incident response team should discuss information sharing with

the organization’s public affairs office, legal department, and management before an incident occurs to

establish policies and procedures regarding information sharing. Otherwise, sensitive information

regarding incidents may be provided to unauthorized parties, potentially leading to additional disruption

and financial loss. The team should document all contacts and communications with outside parties for

liability and evidentiary purposes.

The following sections provide guidelines on communicating with several types of outside parties, as

depicted in Figure 2-1. The double-headed arrows indicate that either party may initiate communications.

See Section 4 for additional information on communicating with outside parties, and see Section 2.4 for a

discussion of communications involving incident response outsourcers.

COMPUTER SECURITY INCIDENT HANDLING GUIDE

Figure 2-1. Communications with Outside Parties

2.3.4.1 The Media

The incident handling team should establish media communications procedures that comply with the

organization’s policies on media interaction and information disclosure.

For discussing incidents with the

media, organizations often find it beneficial to designate a single point of contact (POC) and at least one

backup contact. The following actions are recommended for preparing these designated contacts and

should also be considered for preparing others who may be communicating with the media:

 Conduct training sessions on interacting with the media regarding incidents, which should include the

importance of not revealing sensitive information, such as technical details of countermeasures that

could assist other attackers, and the positive aspects of communicating important information to the

public fully and effectively.

 Establish procedures to brief media contacts on the issues and sensitivities regarding a particular

incident before discussing it with the media.

For example, an organization may want members of its public affairs office and legal department to participate in all

incident discussions with the media.

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 Maintain a statement of the current status of the incident so that communications with the media are

consistent and up-to-date.

 Remind all staff of the general procedures for handling media inquiries.

 Hold mock interviews and press conferences during incident handling exercises. The following are

examples of questions to ask the media contact:

– Who attacked you? Why?

– When did it happen? How did it happen? Did this happen because you have poor security

practices?

– How widespread is this incident? What steps are you taking to determine what happened and to

prevent future occurrences?

– What is the impact of this incident? Was any personally identifiable information (PII) exposed?

What is the estimated cost of this incident?

2.3.4.2 Law Enforcement

One reason that many security-related incidents do not result in convictions is that some organizations do

not properly contact law enforcement. Several levels of law enforcement are available to investigate

incidents: for example, within the United States, Federal investigatory agencies (e.g., the Federal Bureau

of Investigation [FBI] and the U.S. Secret Service), district attorney offices, state law enforcement, and

local (e.g., county) law enforcement. Law enforcement agencies in other countries may also be involved,

such as for attacks launched from or directed at locations outside the US. In addition, agencies have an

Office of Inspector General (OIG) for investigation of violation of the law within each agency. The

incident response team should become acquainted with its various law enforcement representatives before

an incident occurs to discuss conditions under which incidents should be reported to them, how the

reporting should be performed, what evidence should be collected, and how it should be collected.

Law enforcement should be contacted through designated individuals in a manner consistent with the

requirements of the law and the organization’s procedures. Many organizations prefer to appoint one

incident response team member as the primary POC with law enforcement. This person should be familiar

with the reporting procedures for all relevant law enforcement agencies and well prepared to recommend

which agency, if any, should be contacted. Note that the organization typically should not contact

multiple agencies because doing so might result in jurisdictional conflicts. The incident response team

should understand what the potential jurisdictional issues are (e.g., physical location—an organization

based in one state has a server located in a second state attacked from a system in a third state, being used

remotely by an attacker in a fourth state).

2.3.4.3 Incident Reporting Organizations

FISMA requires Federal agencies to report incidents to the United States Computer Emergency Readiness

Team (US-CERT),

which is a governmentwide incident response organization that assists Federal

civilian agencies in their incident handling efforts. US-CERT does not replace existing agency response

teams; rather, it augments the efforts of Federal civilian agencies by serving as a focal point for dealing

with incidents. US-CERT analyzes the agency-provided information to identify trends and indicators of

attacks; these are easier to discern when reviewing data from many organizations than when reviewing

the data of a single organization.

http://www.us-cert.gov/

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Each agency must designate a primary and secondary POC with US-CERT and report all incidents

consistent with the agency’s incident response policy. Organizations should create a policy that states

who is designated to report incidents and how the incidents should be reported. Requirements, categories,

and timeframes for reporting incidents to US-CERT are on the US-CERT website.

All Federal agencies

must ensure that their incident response procedures adhere to US-CERT’s reporting requirements and that

the procedures are followed properly.

All organizations are encouraged to report incidents to their appropriate CSIRTs. If an organization does

not have its own CSIRT to contact, it can report incidents to other organizations, including Information

Sharing and Analysis Centers (ISACs). One of the functions of these industry-specific private sector

groups is to share important computer security-related information among their members. Several ISACs

have been formed for industry sectors such as Communications, Electric Sector, Financial Services,

Information Technology, and Research and Education.

2.3.4.4 Other Outside Parties

An organization may want to discuss incidents with other groups, including those listed below. When

reaching out to these external parties, an organization may want to work through US-CERT or its ISAC,

as a “trusted introducer” to broker the relationship. It is likely that others are experiencing similar issues,

and the trusted introducer can ensure that any such patterns are identified and taken into consideration.

 Organization’s ISP. An organization may need assistance from its ISP in blocking a major network-

based attack or tracing its origin.

 Owners of Attacking Addresses. If attacks are originating from an external organization’s IP

address space, incident handlers may want to talk to the designated security contacts for the

organization to alert them to the activity or to ask them to collect evidence. It is highly recommended

to coordinate such communications with US-CERT or an ISAC.

 Software Vendors. Incident handlers may want to speak to a software vendor about suspicious

activity. This contact could include questions regarding the significance of certain log entries or

known false positives for certain intrusion detection signatures, where minimal information regarding

the incident may need to be revealed. More information may need to be provided in some cases—for

example, if a server appears to have been compromised through an unknown software vulnerability.

Software vendors may also provide information on known threats (e.g., new attacks) to help

organizations understand the current threat environment.

 Other Incident Response Teams. An organization may experience an incident that is similar to ones

handled by other teams; proactively sharing information can facilitate more effective and efficient

incident handling (e.g., providing advance warning, increasing preparedness, developing situational

awareness). Groups such as the Forum of Incident Response and Security Teams (FIRST)

, the

Government Forum of Incident Response and Security Teams (GFIRST)

, and the Anti-Phishing

Working Group (APWG)

are not incident response teams, but they promote information sharing

among incident response teams.

 Affected External Parties. An incident may affect external parties directly—for example, an outside

organization may contact the organization and claim that one of the organization’s users is attacking

http://www.us-cert.gov/federal/reportingRequirements.html

See the National Council of ISACs website at http://www.isaccouncil.org/ for a list of ISACs.

http://www.first.org/

GFIRST is specifically for Federal departments and agencies. (http://www.us-cert.gov/federal/gfirst.html)

http://www.antiphishing.org/

COMPUTER SECURITY INCIDENT HANDLING GUIDE

it. Another way in which external parties may be affected is if an attacker gains access to sensitive

information regarding them, such as credit card information. In some jurisdictions, organizations are

required to notify all parties that are affected by such an incident. Regardless of the circumstances, it

is preferable for the organization to notify affected external parties of an incident before the media or

other external organizations do so. Handlers should be careful to give out only appropriate

information—the affected parties may request details about internal investigations that should not be

revealed publicly.

OMB Memorandum M-07-16, Safeguarding Against and Responding to the Breach of Personally

Identifiable Information, requires Federal agencies to develop and implement a breach notification

policy for personally identifiable information (PII).

Incident handlers should understand how their

incident handling actions should differ when a PII breach is suspected to have occurred, such as

notifying additional parties or notifying parties within a shorter timeframe. Specific recommendations

for PII breach notification policies are presented in OMB Memorandum M-07-16. Also, the National

Conference of State Legislatures has a list of state security breach notification laws.

2.4 Incident Response Team Structure

An incident response team should be available for anyone who discovers or suspects that an incident

involving the organization has occurred. One or more team members, depending on the magnitude of the

incident and availability of personnel, will then handle the incident. The incident handlers analyze the

incident data, determine the impact of the incident, and act appropriately to limit the damage and restore

normal services. The incident response team’s success depends on the participation and cooperation of

individuals throughout the organization. This section identifies such individuals, discusses incident

response team models, and provides advice on selecting an appropriate model.

2.4.1 Team Models

Possible structures for an incident response team include the following:

 Central Incident Response Team. A single incident response team handles incidents throughout the

organization. This model is effective for small organizations and for organizations with minimal

geographic diversity in terms of computing resources.

 Distributed Incident Response Teams. The organization has multiple incident response teams, each

responsible for a particular logical or physical segment of the organization. This model is effective for

large organizations (e.g., one team per division) and for organizations with major computing

resources at distant locations (e.g., one team per geographic region, one team per major facility).

However, the teams should be part of a single coordinated entity so that the incident response process

is consistent across the organization and information is shared among teams. This is particularly

important because multiple teams may see components of the same incident or may handle similar

incidents.

 Coordinating Team. An incident response team provides advice to other teams without having

authority over those teams—for example, a departmentwide team may assist individual agencies’

teams. This model can be thought of as a CSIRT for CSIRTs. Because the focus of this document is

http://www.whitehouse.gov/omb/memoranda/fy2007/m07-16.pdf

http://www.ncsl.org/default.aspx?tabid=13489

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central and distributed CSIRTs, the coordinating team model is not addressed in detail in this

document.

Incident response teams can also use any of three staffing models:

 Employees. The organization performs all of its incident response work, with limited technical and

administrative support from contractors.

 Partially Outsourced. The organization outsources portions of its incident response work.

Section 2.4.2 discusses the major factors that should be considered with outsourcing. Although

incident response duties can be divided among the organization and one or more outsourcers in many

ways, a few arrangements have become commonplace:

– The most prevalent arrangement is for the organization to outsource 24-hours-a-day, 7-days-a-

week (24/7) monitoring of intrusion detection sensors, firewalls, and other security devices to an

offsite managed security services provider (MSSP). The MSSP identifies and analyzes suspicious

activity and reports each detected incident to the organization’s incident response team.

– Some organizations perform basic incident response work in-house and call on contractors to

assist with handling incidents, particularly those that are more serious or widespread.

 Fully Outsourced. The organization completely outsources its incident response work, typically to

an onsite contractor. This model is most likely to be used when the organization needs a full-time,

onsite incident response team but does not have enough available, qualified employees. It is assumed

that the organization will have employees supervising and overseeing the outsourcer’s work.

2.4.2 Team Model Selection

When selecting appropriate structure and staffing models for an incident response team, organizations

should consider the following factors:

 The Need for 24/7 Availability. Most organizations need incident response staff to be available 24/7.

This typically means that incident handlers can be contacted by phone, but it can also mean that an

onsite presence is required. Real-time availability is the best for incident response because the longer

an incident lasts, the more potential there is for damage and loss. Real-time contact is often needed

when working with other organizations—for example, tracing an attack back to its source.

 Full-Time Versus Part-Time Team Members. Organizations with limited funding, staffing, or

incident response needs may have only part-time incident response team members, serving as more of

a virtual incident response team. In this case, the incident response team can be thought of as a

volunteer fire department. When an emergency occurs, the team members are contacted rapidly, and

those who can assist do so. An existing group such as the IT help desk can act as a first POC for

incident reporting. The help desk members can be trained to perform the initial investigation and data

gathering and then alert the incident response team if it appears that a serious incident has occurred.

 Employee Morale. Incident response work is very stressful, as are the on-call responsibilities of most

team members. This combination makes it easy for incident response team members to become

overly stressed. Many organizations will also struggle to find willing, available, experienced, and

properly skilled people to participate, particularly in 24-hour support. Segregating roles, particularly

Information about the Coordinating team model, as well as extensive information on other team models, is available in a

CERT®/CC document titled Organizational Models for Computer Security Incident Response Teams (CSIRTs)

(http://www.cert.org/archive/pdf/03hb001.pdf).

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reducing the amount of administrative work that team members are responsible for performing, can

be a significant boost to morale.

 Cost. Cost is a major factor, especially if employees are required to be onsite 24/7. Organizations

may fail to include incident response-specific costs in budgets, such as sufficient funding for training

and maintaining skills. Because the incident response team works with so many facets of IT, its

members need much broader knowledge than most IT staff members. They must also understand how

to use the tools of incident response, such as digital forensics software. Other costs that may be

overlooked are physical security for the team’s work areas and communications mechanisms.

 Staff Expertise. Incident handling requires specialized knowledge and experience in several

technical areas; the breadth and depth of knowledge required varies based on the severity of the

organization’s risks. Outsourcers may possess deeper knowledge of intrusion detection, forensics,

vulnerabilities, exploits, and other aspects of security than employees of the organization. Also,

MSSPs may be able to correlate events among customers so that they can identify new threats more

quickly than any individual customer could. However, technical staff members within the

organization usually have much better knowledge of the organization’s environment than an

outsourcer would, which can be beneficial in identifying false positives associated with organization-

specific behavior and the criticality of targets. Section 2.4.3 contains additional information on

recommended team member skills.

When considering outsourcing, organizations should keep these issues in mind:

 Current and Future Quality of Work. Organizations should consider not only the current quality

(breadth and depth) of the outsourcer’s work, but also efforts to ensure the quality of future work—

for example, minimizing turnover and burnout and providing a solid training program for new

employees. Organizations should think about how they could objectively assess the quality of the

outsourcer’s work.

 Division of Responsibilities. Organizations are often unwilling to give an outsourcer authority to

make operational decisions for the environment (e.g., disconnecting a web server). It is important to

document the appropriate actions for these decision points. For example, one partially outsourced

model addresses this issue by having the outsourcer provide incident data to the organization’s

internal team, along with recommendations for further handling the incident. The internal team

ultimately makes the operational decisions, with the outsourcer continuing to provide support as

needed.

 Sensitive Information Revealed to the Contractor. Dividing incident response responsibilities and

restricting access to sensitive information can limit this. For example, a contractor may determine

what user ID was used in an incident (e.g., ID 123456) but not know what person is associated with

the user ID. Employees can then take over the investigation. Non-disclosure agreements (NDAs) are

one possible option for protecting the disclosure of sensitive information.

 Lack of Organization-Specific Knowledge. Accurate analysis and prioritization of incidents are

dependent on specific knowledge of the organization’s environment. The organization should provide

the outsourcer regularly updated documents that define what incidents it is concerned about, which

resources are critical, and what the level of response should be under various sets of circumstances.

The organization should also report all changes and updates made to its IT infrastructure, network

configuration, and systems. Otherwise, the contractor has to make a best guess as to how each

incident should be handled, inevitably leading to mishandled incidents and frustration on both sides.

Lack of organization-specific knowledge can also be a problem when incident response is not

outsourced if communications are weak among teams or if the organization simply does not collect

the necessary information.

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 Lack of Correlation. Correlation among multiple data sources is very important. If the intrusion

detection system records an attempted attack against a web server, but the outsourcer has no access to

the server’s logs, it may be unable to determine whether the attack was successful. To be efficient, the

outsourcer will require administrative privileges to critical systems and security device logs remotely

over a secure channel. This will increase administration costs, introduce additional access entry

points, and increase the risk of unauthorized disclosure of sensitive information.

 Handling Incidents at Multiple Locations. Effective incident response work often requires a

physical presence at the organization’s facilities. If the outsourcer is offsite, consider where the

outsourcer is located, how quickly it can have an incident response team at any facility, and how

much this will cost. Consider onsite visits; perhaps there are certain facilities or areas where the

outsourcer should not be permitted to work.

 Maintaining Incident Response Skills In-House. Organizations that completely outsource incident

response should strive to maintain basic incident response skills in-house. Situations may arise in

which the outsourcer is unavailable, so the organization should be prepared to perform its own

incident handling. The organization’s technical staff must also be able to understand the significance,

technical implications, and impact of the outsourcer’s recommendations.

2.4.3 Incident Response Personnel

A single employee, with one or more designated alternates, should be in charge of incident response. In a

fully outsourced model, this person oversees and evaluates the outsourcer’s work. All other models

generally have a team manager and one or more deputies who assumes authority in the absence of the

team manager. The managers typically perform a variety of tasks, including acting as a liaison with upper

management and other teams and organizations, defusing crisis situations, and ensuring that the team has

the necessary personnel, resources, and skills. Managers should be technically adept and have excellent

communication skills, particularly an ability to communicate to a range of audiences. Managers are

ultimately responsible for ensuring that incident response activities are performed properly.

In addition to the team manager and deputy, some teams also have a technical lead—a person with strong

technical skills and incident response experience who assumes oversight of and final responsibility for the

quality of the team’s technical work. The position of technical lead should not be confused with the

position of incident lead. Larger teams often assign an incident lead as the primary POC for handling a

specific incident; the incident lead is held accountable for the incident’s handling. Depending on the size

of the incident response team and the magnitude of the incident, the incident lead may not actually

perform any actual incident handling, but rather coordinate the handlers’ activities, gather information

from the handlers, provide incident updates to other groups, and ensure that the team’s needs are met.

Members of the incident response team should have excellent technical skills, such as system

administration, network administration, programming, technical support, or intrusion detection. Every

team member should have good problem solving skills and critical thinking abilities. It is not necessary

for every team member to be a technical expert—to a large degree, practical and funding considerations

will dictate this—but having at least one highly proficient person in each major area of technology (e.g.,

commonly attacked operating systems and applications) is a necessity. It may also be helpful to have

some team members specialize in particular technical areas, such as network intrusion detection, malware

analysis, or forensics. It is also often helpful to temporarily bring in technical specialists that aren’t

normally part of the team.

It is important to counteract staff burnout by providing opportunities for learning and growth. Suggestions

for building and maintaining skills are as follows:

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 Budget enough funding to maintain, enhance, and expand proficiency in technical areas and security

disciplines, as well as less technical topics such as the legal aspects of incident response. This should

include sending staff to conferences and encouraging or otherwise incentivizing participation in

conferences, ensuring the availability of technical references that promote deeper technical

understanding, and occasionally bringing in outside experts (e.g., contractors) with deep technical

knowledge in needed areas as funding permits.

 Give team members opportunities to perform other tasks, such as creating educational materials,

conducting security awareness workshops, and performing research.

 Consider rotating staff members in and out of the incident response team, and participate in

exchanges in which team members temporarily trade places with others (e.g., network administrators)

to gain new technical skills.

 Maintain sufficient staffing so that team members can have uninterrupted time off work (e.g.,

vacations).

 Create a mentoring program to enable senior technical staff to help less experienced staff learn

incident handling.

 Develop incident handling scenarios and have the team members discuss how they would handle

them. Appendix A contains a set of scenarios and a list of questions to be used during scenario

discussions.

Incident response team members should have other skills in addition to technical expertise. Teamwork

skills are of fundamental importance because cooperation and coordination are necessary for successful

incident response. Every team member should also have good communication skills. Speaking skills are

important because the team will interact with a wide variety of people, and writing skills are important

when team members are preparing advisories and procedures. Although not everyone within a team needs

to have strong writing and speaking skills, at least a few people within every team should possess them so

the team can represent itself well in front of others.

2.4.4 Dependencies within Organizations

It is important to identify other groups within the organization that may need to participate in incident

handling so that their cooperation can be solicited before it is needed. Every incident response team relies

on the expertise, judgment, and abilities of others, including:

 Management. Management establishes incident response policy, budget, and staffing. Ultimately,

management is held responsible for coordinating incident response among various stakeholders,

minimizing damage, and reporting to Congress, OMB, the General Accounting Office (GAO), and

other parties.

 Information Assurance. Information security staff members may be needed during certain stages of

incident handling (prevention, containment, eradication, and recovery)—for example, to alter network

security controls (e.g., firewall rulesets).

 IT Support. IT technical experts (e.g., system and network administrators) not only have the needed

skills to assist but also usually have the best understanding of the technology they manage on a daily

basis. This understanding can ensure that the appropriate actions are taken for the affected system,

such as whether to disconnect an attacked system.

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 Legal Department. Legal experts should review incident response plans, policies, and procedures to

ensure their compliance with law and Federal guidance, including the right to privacy. In addition, the

guidance of the general counsel or legal department should be sought if there is reason to believe that

an incident may have legal ramifications, including evidence collection, prosecution of a suspect, or a

lawsuit, or if there may be a need for a memorandum of understanding (MOU) or other binding

agreements involving liability limitations for information sharing.

 Public Affairs and Media Relations. Depending on the nature and impact of an incident, a need may

exist to inform the media and, by extension, the public.

 Human Resources. If an employee is suspected of causing an incident, the human resources

department may be involved—for example, in assisting with disciplinary proceedings.

 Business Continuity Planning. Organizations should ensure that incident response policies and

procedures and business continuity processes are in sync. Computer security incidents undermine the

business resilience of an organization. Business continuity planning professionals should be made

aware of incidents and their impacts so they can fine-tune business impact assessments, risk

assessments, and continuity of operations plans. Further, because business continuity planners have

extensive expertise in minimizing operational disruption during severe circumstances, they may be

valuable in planning responses to certain situations, such as denial of service (DoS) conditions.

 Physical Security and Facilities Management. Some computer security incidents occur through

breaches of physical security or involve coordinated logical and physical attacks. The incident

response team also may need access to facilities during incident handling—for example, to acquire a

compromised workstation from a locked office.

2.5 Incident Response Team Services

The main focus of an incident response team is performing incident response, but it is fairly rare for a

team to perform incident response only. The following are examples of other services a team might offer:

 Intrusion Detection. The first tier of an incident response team often assumes responsibility for

intrusion detection.

The team generally benefits because it should be poised to analyze incidents

more quickly and accurately, based on the knowledge it gains of intrusion detection technologies.

 Advisory Distribution. A team may issue advisories within the organization regarding new

vulnerabilities and threats.

Automated methods should be used whenever appropriate to disseminate

information; for example, the National Vulnerability Database (NVD) provides information via XML

and RSS feeds when new vulnerabilities are added to it.

Advisories are often most necessary when

new threats are emerging, such as a high-profile social or political event (e.g., celebrity wedding) that

attackers are likely to leverage in their social engineering. Only one group within the organization

should distribute computer security advisories to avoid duplicated effort and conflicting information.

 Education and Awareness. Education and awareness are resource multipliers—the more the users

and technical staff know about detecting, reporting, and responding to incidents, the less drain there

See NIST SP 800-94, Guide to Intrusion Detection and Prevention Systems (IDPS) for more information on IDPS

technologies. It is available at http://csrc.nist.gov/publications/PubsSPs.html#800-94.

Teams should word advisories so that they do not blame any person or organization for security issues. Teams should meet

with legal advisors to discuss the possible need for a disclaimer in advisories, stating that the team and organization has no

liability in regard to the accuracy of the advisory. This is most pertinent when advisories may be sent to contractors,

vendors, and other nonemployees who are users of the organization’s computing resources.

http://nvd.nist.gov/

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should be on the incident response team. This information can be communicated through many

means: workshops, websites, newsletters, posters, and even stickers on monitors and laptops.

 Information Sharing. Incident response teams often participate in information sharing groups, such

as ISACs or regional partnerships. Accordingly, incident response teams often manage the

organization’s incident information sharing efforts, such as aggregating information related to

incidents and effectively sharing that information with other organizations, as well as ensuring that

pertinent information is shared within the enterprise.

2.6 Recommendations

The key recommendations presented in this section for organizing a computer security incident handling

capability are summarized below.

 Establish a formal incident response capability. Organizations should be prepared to respond

quickly and effectively when computer security defenses are breached. FISMA requires Federal

agencies to establish incident response capabilities.

 Create an incident response policy. The incident response policy is the foundation of the incident

response program. It defines which events are considered incidents, establishes the organizational

structure for incident response, defines roles and responsibilities, and lists the requirements for

reporting incidents, among other items.

 Develop an incident response plan based on the incident response policy. The incident response

plan provides a roadmap for implementing an incident response program based on the organization’s

policy. The plan indicates both short- and long-term goals for the program, including metrics for

measuring the program. The incident response plan should also indicate how often incident handlers

should be trained and the requirements for incident handlers.

 Develop incident response procedures. The incident response procedures provide detailed steps for

responding to an incident. The procedures should cover all the phases of the incident response

process. The procedures should be based on the incident response policy and plan.

 Establish policies and procedures regarding incident-related information sharing. The

organization should communicate appropriate incident details with outside parties, such as the media,

law enforcement agencies, and incident reporting organizations. The incident response team should

discuss this with the organization’s public affairs office, legal department, and management to

establish policies and procedures regarding information sharing. The team should comply with

existing organization policy on interacting with the media and other outside parties.

 Provide pertinent information on incidents to the appropriate organization. Federal civilian

agencies are required to report incidents to US-CERT; other organizations can contact US-CERT

and/or their ISAC. Reporting is beneficial because US-CERT and the ISACs use the reported data to

provide information to the reporting parties regarding new threats and incident trends.

 Consider the relevant factors when selecting an incident response team model. Organizations

should carefully weigh the advantages and disadvantages of each possible team structure model and

staffing model in the context of the organization’s needs and available resources.

 Select people with appropriate skills for the incident response team. The credibility and

proficiency of the team depend to a large extent on the technical skills and critical thinking abilities of

its members. Critical technical skills include system administration, network administration,

programming, technical support, and intrusion detection. Teamwork and communications skills are

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also needed for effective incident handling. Necessary training should be provided to all team

members.

 Identify other groups within the organization that may need to participate in incident handling.

Every incident response team relies on the expertise, judgment, and abilities of other teams, including

management, information assurance, IT support, legal, public affairs, and facilities management.

 Determine which services the team should offer. Although the main focus of the team is incident

response, most teams perform additional functions. Examples include monitoring intrusion detection

sensors, distributing security advisories, and educating users on security.

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3. Handling an Incident

The incident response process has several phases. The initial phase involves establishing and training an

incident response team, and acquiring the necessary tools and resources. During preparation, the

organization also attempts to limit the number of incidents that will occur by selecting and implementing

a set of controls based on the results of risk assessments. However, residual risk will inevitably persist

after controls are implemented. Detection of security breaches is thus necessary to alert the organization

whenever incidents occur. In keeping with the severity of the incident, the organization can mitigate the

impact of the incident by containing it and ultimately recovering from it. During this phase, activity often

cycles back to detection and analysis—for example, to see if additional hosts are infected by malware

while eradicating a malware incident. After the incident is adequately handled, the organization issues a

report that details the cause and cost of the incident and the steps the organization should take to prevent

future incidents. This section describes the major phases of the incident response process—preparation,

detection and analysis, containment, eradication and recovery, and post-incident activity—in detail.

Figure 3-1 illustrates the incident response life cycle.

Figure 3-1. Incident Response Life Cycle

3.1 Preparation

Incident response methodologies typically emphasize preparation—not only establishing an incident

response capability so that the organization is ready to respond to incidents, but also preventing incidents

by ensuring that systems, networks, and applications are sufficiently secure. Although the incident

response team is not typically responsible for incident prevention, it is fundamental to the success of

incident response programs. This section provides basic advice on preparing to handle incidents and on

preventing incidents.

3.1.1 Preparing to Handle Incidents

The lists below provide examples of tools and resources available that may be of value during incident

handling. These lists are intended to be a starting point for discussions about which tools and resources an

organization’s incident handlers need. For example, smartphones are one way to have resilient emergency

COMPUTER SECURITY INCIDENT HANDLING GUIDE

communication and coordination mechanisms. An organization should have multiple (separate and

different) communication and coordination mechanisms in case of failure of one mechanism.

Incident Handler Communications and Facilities:

 Contact information for team members and others within and outside the organization (primary and

backup contacts), such as law enforcement and other incident response teams; information may

include phone numbers, email addresses, public encryption keys (in accordance with the encryption

software described below), and instructions for verifying the contact’s identity

 On-call information for other teams within the organization, including escalation information

 Incident reporting mechanisms, such as phone numbers, email addresses, online forms, and secure

instant messaging systems that users can use to report suspected incidents; at least one mechanism

should permit people to report incidents anonymously

 Issue tracking system for tracking incident information, status, etc.

 Smartphones to be carried by team members for off-hour support and onsite communications

 Encryption software to be used for communications among team members, within the organization

and with external parties; for Federal agencies, software must use a FIPS-validated encryption

algorithm

 War room for central communication and coordination; if a permanent war room is not necessary or

practical, the team should create a procedure for procuring a temporary war room when needed

 Secure storage facility for securing evidence and other sensitive materials

Incident Analysis Hardware and Software:

 Digital forensic workstations

and/or backup devices to create disk images, preserve log files, and

save other relevant incident data

 Laptops for activities such as analyzing data, sniffing packets, and writing reports

 Spare workstations, servers, and networking equipment, or the virtualized equivalents, which

may be used for many purposes, such as restoring backups and trying out malware

 Blank removable media

 Portable printer to print copies of log files and other evidence from non-networked systems

 Packet sniffers and protocol analyzers to capture and analyze network traffic

 Digital forensic software to analyze disk images

 Removable media with trusted versions of programs to be used to gather evidence from systems

 Evidence gathering accessories, including hard-bound notebooks, digital cameras, audio recorders,

chain of custody forms, evidence storage bags and tags, and evidence tape, to preserve evidence for

possible legal actions

FIPS 140-2, Security Requirements for Cryptographic Modules, http://csrc.nist.gov/publications/PubsFIPS.html.

A digital forensic workstation is specially designed to assist incident handlers in acquiring and analyzing data. These

workstations typically contain a set of removable hard drives that can be used for evidence storage.

COMPUTER SECURITY INCIDENT HANDLING GUIDE

Incident Analysis Resources:

 Port lists, including commonly used ports and Trojan horse ports

 Documentation for OSs, applications, protocols, and intrusion detection and antivirus products

 Network diagrams and lists of critical assets, such as database servers

 Current baselines of expected network, system, and application activity

 Cryptographic hashes of critical files

to speed incident analysis, verification, and eradication

Incident Mitigation Software:

 Access to images of clean OS and application installations for restoration and recovery purposes

Many incident response teams create a jump kit, which is a portable case that contains materials that may

be needed during an investigation. The jump kit should be ready to go at all times. Jump kits contain

many of the same items listed in the bulleted lists above. For example, each jump kit typically includes a

laptop, loaded with appropriate software (e.g., packet sniffers, digital forensics). Other important

materials include backup devices, blank media, and basic networking equipment and cables. Because the

purpose of having a jump kit is to facilitate faster responses, the team should avoid borrowing items from

the jump kit.

Each incident handler should have access to at least two computing devices (e.g., laptops). One, such as

the one from the jump kit, should be used to perform packet sniffing, malware analysis, and all other

actions that risk contaminating the laptop that performs them. This laptop should be scrubbed and all

software reinstalled before it is used for another incident. Note that because this laptop is special purpose,

it is likely to use software other than the standard enterprise tools and configurations, and whenever

possible the incident handlers should be allowed to specify basic technical requirements for these special-

purpose investigative laptops. In addition to an investigative laptop, each incident handler should also

have a standard laptop, smart phone, or other computing device for writing reports, reading email, and

performing other duties unrelated to the hands-on incident analysis.

Exercises involving simulated incidents can also be very useful for preparing staff for incident handling;

see NIST SP 800-84 for more information on exercises

and Appendix A for sample exercise scenarios.

3.1.2 Preventing Incidents

Keeping the number of incidents reasonably low is very important to protect the business processes of the

organization. If security controls are insufficient, higher volumes of incidents may occur, overwhelming

the incident response team. This can lead to slow and incomplete responses, which translate to a larger

negative business impact (e.g., more extensive damage, longer periods of service and data unavailability).

It is outside the scope of this document to provide specific advice on securing networks, systems, and

applications. Although incident response teams are generally not responsible for securing resources, they

can be advocates of sound security practices. An incident response team may be able to identify problems

that the organization is otherwise not aware of; the team can play a key role in risk assessment and

training by identifying gaps. Other documents already provide advice on general security concepts and

The National Software Reference Library (NSRL) Project maintains records of hashes of various files, including operating

system, application, and graphic image files. The hashes can be downloaded from http://www.nsrl.nist.gov/.

Guide to Test, Training, and Exercise Programs for IT Plans and Capabilities,

http://csrc.nist.gov/publications/PubsSPs.html#800-84

COMPUTER SECURITY INCIDENT HANDLING GUIDE

operating system and application-specific guidelines.

The following text, however, provides a brief

overview of some of the main recommended practices for securing networks, systems, and applications:

 Risk Assessments. Periodic risk assessments of systems and applications should determine what

risks are posed by combinations of threats and vulnerabilities.

This should include understanding the

applicable threats, including organization-specific threats. Each risk should be prioritized, and the

risks can be mitigated, transferred, or accepted until a reasonable overall level of risk is reached.

Another benefit of conducting risk assessments regularly is that critical resources are identified,

allowing staff to emphasize monitoring and response activities for those resources.

 Host Security. All hosts should be hardened appropriately using standard configurations. In addition

to keeping each host properly patched, hosts should be configured to follow the principle of least

privilege—granting users only the privileges necessary for performing their authorized tasks. Hosts

should have auditing enabled and should log significant security-related events. The security of hosts

and their configurations should be continuously monitored.

Many organizations use Security

Content Automation Protocol (SCAP)

expressed operating system and application configuration

checklists to assist in securing hosts consistently and effectively.

 Network Security. The network perimeter should be configured to deny all activity that is not

expressly permitted. This includes securing all connection points, such as virtual private networks

(VPNs) and dedicated connections to other organizations.

 Malware Prevention. Software to detect and stop malware should be deployed throughout the

organization. Malware protection should be deployed at the host level (e.g., server and workstation

operating systems), the application server level (e.g., email server, web proxies), and the application

client level (e.g., email clients, instant messaging clients).

 User Awareness and Training. Users should be made aware of policies and procedures regarding

appropriate use of networks, systems, and applications. Applicable lessons learned from previous

incidents should also be shared with users so they can see how their actions could affect the

organization. Improving user awareness regarding incidents should reduce the frequency of incidents.

IT staff should be trained so that they can maintain their networks, systems, and applications in

accordance with the organization’s security standards.

http://csrc.nist.gov/publications/PubsSPs.html provides links to the NIST Special Publications on computer security, which

include documents on operating system and application security baselines.

Guidelines on risk assessment are available in NIST SP 800-30, Guide for Conducting Risk Assessments, at

http://csrc.nist.gov/publications/PubsSPs.html#800-30-Rev1.

Information on identifying critical resources is discussed in FIPS 199, Standards for Security Categorization of Federal

Information and Information Systems, at http://csrc.nist.gov/publications/PubsFIPS.html.

For more information on continuous monitoring, see NIST SP 800-137, Information Security Continuous Monitoring for

Federal Information Systems and Organizations (http://csrc.nist.gov/publications/PubsSPs.html#800-137).

More information on SCAP is available from NIST SP 800-117 Revision 1, Guide to Adopting and Using the Security

Content Automation Protocol (SCAP) Version 1.2 (http://csrc.nist.gov/publications/PubsSPs.html#800-117).

NIST hosts a security checklists repository at http://checklists.nist.gov/.

More information on malware prevention is available from NIST SP 800-83, Guide to Malware Incident Prevention and

Handling (http://csrc.nist.gov/publications/PubsSPs.html#800-83).

COMPUTER SECURITY INCIDENT HANDLING GUIDE

3.2 Detection and Analysis

Figure 3-2. Incident Response Life Cycle (Detection and Analysis)

3.2.1 Attack Vectors

Incidents can occur in countless ways, so it is infeasible to develop step-by-step instructions for handling

every incident. Organizations should be generally prepared to handle any incident but should focus on

being prepared to handle incidents that use common attack vectors. Different types of incidents merit

different response strategies. The attack vectors listed below are not intended to provide definitive

classification for incidents; rather, they simply list common methods of attack, which can be used as a

basis for defining more specific handling procedures.

 External/Removable Media: An attack executed from removable media or a peripheral device—for

example, malicious code spreading onto a system from an infected USB flash drive.

 Attrition: An attack that employs brute force methods to compromise, degrade, or destroy systems,

networks, or services (e.g., a DDoS intended to impair or deny access to a service or application; a

brute force attack against an authentication mechanism, such as passwords, CAPTCHAS, or digital

signatures).

 Web: An attack executed from a website or web-based application—for example, a cross-site

scripting attack used to steal credentials or a redirect to a site that exploits a browser vulnerability and

installs malware.

 Email: An attack executed via an email message or attachment—for example, exploit code disguised

as an attached document or a link to a malicious website in the body of an email message.

 Impersonation: An attack involving replacement of something benign with something malicious—

for example, spoofing, man in the middle attacks, rogue wireless access points, and SQL injection

attacks all involve impersonation.

 Improper Usage: Any incident resulting from violation of an organization’s acceptable usage

policies by an authorized user, excluding the above categories; for example, a user installs file sharing

software, leading to the loss of sensitive data; or a user performs illegal activities on a system.

COMPUTER SECURITY INCIDENT HANDLING GUIDE

 Loss or Theft of Equipment: The loss or theft of a computing device or media used by the

organization, such as a laptop, smartphone, or authentication token.

 Other: An attack that does not fit into any of the other categories.

This section focuses on recommended practices for handling any type of incident. It is outside the scope

of this publication to give specific advice based on the attack vectors; such guidelines would be provided

in separate publications addressing other incident handling topics, such as NIST SP 800-83 on malware

incident prevention and handling.

3.2.2 Signs of an Incident

For many organizations, the most challenging part of the incident response process is accurately detecting

and assessing possible incidents—determining whether an incident has occurred and, if so, the type,

extent, and magnitude of the problem. What makes this so challenging is a combination of three factors:

 Incidents may be detected through many different means, with varying levels of detail and fidelity.

Automated detection capabilities include network-based and host-based IDPSs, antivirus software,

and log analyzers. Incidents may also be detected through manual means, such as problems reported

by users. Some incidents have overt signs that can be easily detected, whereas others are almost

impossible to detect.

 The volume of potential signs of incidents is typically high—for example, it is not uncommon for an

organization to receive thousands or even millions of intrusion detection sensor alerts per day. (See

Section 3.2.4 for information on analyzing such alerts.)

 Deep, specialized technical knowledge and extensive experience are necessary for proper and

efficient analysis of incident-related data.

Signs of an incident fall into one of two categories: precursors and indicators. A precursor is a sign that

an incident may occur in the future. An indicator is a sign that an incident may have occurred or may be

occurring now.

Most attacks do not have any identifiable or detectable precursors from the target’s perspective. If

precursors are detected, the organization may have an opportunity to prevent the incident by altering its

security posture to save a target from attack. At a minimum, the organization could monitor activity

involving the target more closely. Examples of precursors are:

 Web server log entries that show the usage of a vulnerability scanner

 An announcement of a new exploit that targets a vulnerability of the organization’s mail server

 A threat from a group stating that the group will attack the organization.

While precursors are relatively rare, indicators are all too common. Too many types of indicators exist to

exhaustively list them, but some examples are listed below:

 A network intrusion detection sensor alerts when a buffer overflow attempt occurs against a database

server.

 Antivirus software alerts when it detects that a host is infected with malware.

 A system administrator sees a filename with unusual characters.

 A host records an auditing configuration change in its log.

COMPUTER SECURITY INCIDENT HANDLING GUIDE

 An application logs multiple failed login attempts from an unfamiliar remote system.

 An email administrator sees a large number of bounced emails with suspicious content.

 A network administrator notices an unusual deviation from typical network traffic flows.

3.2.3 Sources of Precursors and Indicators

Precursors and indicators are identified using many different sources, with the most common being

computer security software alerts, logs, publicly available information, and people. Table 3-2 lists

common sources of precursors and indicators for each category.

Table 3-1. Common Sources of Precursors and Indicators

Source

Description

Alerts

IDPSs

IDPS products identify suspicious events and record pertinent data regarding them, including the

date and time the attack was detected, the type of attack, the source and destination IP

addresses, and the username (if applicable and known). Most IDPS products use attack

signatures to identify malicious activity; the signatures must be kept up to date so that the

newest attacks can be detected. IDPS software often produces false positives—alerts that

indicate malicious activity is occurring, when in fact there has been none. Analysts should

manually validate IDPS alerts either by closely reviewing the recorded supporting data or by

getting related data from other sources.31

SIEMs

Security Information and Event Management (SIEM) products are similar to IDPS products, but

they generate alerts based on analysis of log data (see below).

Antivirus and

antispam

software

Antivirus software detects various forms of malware, generates alerts, and prevents the malware

from infecting hosts. Current antivirus products are effective at stopping many instances of

malware if their signatures are kept up to date. Antispam software is used to detect spam and

prevent it from reaching users’ mailboxes. Spam may contain malware, phishing attacks, and

other malicious content, so alerts from antispam software may indicate attack attempts.

File integrity

checking

software

File integrity checking software can detect changes made to important files during incidents. It

uses a hashing algorithm to obtain a cryptographic checksum for each designated file. If the file

is altered and the checksum is recalculated, an extremely high probability exists that the new

checksum will not match the old checksum. By regularly recalculating checksums and comparing

them with previous values, changes to files can be detected.

Third-party

monitoring

services

Third parties offer a variety of subscription-based and free monitoring services. An example is

fraud detection services that will notify an organization if its IP addresses, domain names, etc.

are associated with current incident activity involving other organizations. There are also free

real-time blacklists with similar information. Another example of a third-party monitoring service

is a CSIRC notification list; these lists are often available only to other incident response teams.

Logs

Operating

system,

service and

application

logs

Logs from operating systems, services, and applications (particularly audit-related data) are

frequently of great value when an incident occurs, such as recording which accounts were

accessed and what actions were performed. Organizations should require a baseline level of

logging on all systems and a higher baseline level on critical systems. Logs can be used for

analysis by correlating event information. Depending on the event information, an alert can be

generated to indicate an incident. Section 3.2.4 discusses the value of centralized logging.

Network

device logs

Logs from network devices such as firewalls and routers are not typically a primary source of

precursors or indicators. Although these devices are usually configured to log blocked

connection attempts, they provide little information about the nature of the activity. Still, they can

be valuable in identifying network trends and in correlating events detected by other devices.

See NIST SP 800-94, Guide to Intrusion Detection and Prevention Systems, for additional information on IDPS products. It

is available at http://csrc.nist.gov/publications/PubsSPs.html#800-94.

COMPUTER SECURITY INCIDENT HANDLING GUIDE

Source

Description

Network flows

A network flow is a particular communication session occurring between hosts. Routers and

other networking devices can provide network flow information, which can be used to find

anomalous network activity caused by malware, data exfiltration, and other malicious acts. There

are many standards for flow data formats, including NetFlow, sFlow, and IPFIX.

Publicly Available Information

Information on

new

vulnerabilities

and exploits

Keeping up with new vulnerabilities and exploits can prevent some incidents from occurring and

assist in detecting and analyzing new attacks. The National Vulnerability Database (NVD)

contains information on vulnerabilities.32 Organizations such as US-CERT33 and CERT®/CC

periodically provide threat update information through briefings, web postings, and mailing lists.

People

People from

within the

organization

Users, system administrators, network administrators, security staff, and others from within the

organization may report signs of incidents. It is important to validate all such reports. One

approach is to ask people who provide such information how confident they are of the accuracy

of the information. Recording this estimate along with the information provided can help

considerably during incident analysis, particularly when conflicting data is discovered.

People from

other

organizations

Reports of incidents that originate externally should be taken seriously. For example, the

organization might be contacted by a party claiming a system at the organization is attacking its

systems. External users may also report other indicators, such as a defaced web page or an

unavailable service. Other incident response teams also may report incidents. It is important to

have mechanisms in place for external parties to report indicators and for trained staff to monitor

those mechanisms carefully; this may be as simple as setting up a phone number and email

address, configured to forward messages to the help desk.

3.2.4 Incident Analysis

Incident detection and analysis would be easy if every precursor or indicator were guaranteed to be

accurate; unfortunately, this is not the case. For example, user-provided indicators such as a complaint of

a server being unavailable are often incorrect. Intrusion detection systems may produce false positives—

incorrect indicators. These examples demonstrate what makes incident detection and analysis so difficult:

each indicator ideally should be evaluated to determine if it is legitimate. Making matters worse, the total

number of indicators may be thousands or millions a day. Finding the real security incidents that occurred

out of all the indicators can be a daunting task.

Even if an indicator is accurate, it does not necessarily mean that an incident has occurred. Some

indicators, such as a server crash or modification of critical files, could happen for several reasons other

than a security incident, including human error. Given the occurrence of indicators, however, it is

reasonable to suspect that an incident might be occurring and to act accordingly. Determining whether a

particular event is actually an incident is sometimes a matter of judgment. It may be necessary to

collaborate with other technical and information security personnel to make a decision. In many instances,

a situation should be handled the same way regardless of whether it is security related. For example, if an

organization is losing Internet connectivity every 12 hours and no one knows the cause, the staff would

want to resolve the problem just as quickly and would use the same resources to diagnose the problem,

regardless of its cause.

Some incidents are easy to detect, such as an obviously defaced web page. However, many incidents are

not associated with such clear symptoms. Small signs such as one change in one system configuration file

may be the only indicators that an incident has occurred. In incident handling, detection may be the most

difficult task. Incident handlers are responsible for analyzing ambiguous, contradictory, and incomplete

symptoms to determine what has happened. Although technical solutions exist that can make detection

http://nvd.nist.gov/

http://www.us-cert.gov/cas/signup.html

COMPUTER SECURITY INCIDENT HANDLING GUIDE

easier, the best remedy is to build a team of highly experienced and proficient staff members who can

analyze the precursors and indicators effectively and efficiently and take appropriate actions. Without a

well-trained and capable staff, incident detection and analysis will be conducted inefficiently, and costly

mistakes will be made.

The incident response team should work quickly to analyze and validate each incident, following a pre-

defined process and documenting each step taken. When the team believes that an incident has occurred,

the team should rapidly perform an initial analysis to determine the incident’s scope, such as which

networks, systems, or applications are affected; who or what originated the incident; and how the incident

is occurring (e.g., what tools or attack methods are being used, what vulnerabilities are being exploited).

The initial analysis should provide enough information for the team to prioritize subsequent activities,

such as containment of the incident and deeper analysis of the effects of the incident.

Performing the initial analysis and validation is challenging. The following are recommendations for

making incident analysis easier and more effective:

 Profile Networks and Systems. Profiling is measuring the characteristics of expected activity so that

changes to it can be more easily identified. Examples of profiling are running file integrity checking

software on hosts to derive checksums for critical files and monitoring network bandwidth usage to

determine what the average and peak usage levels are on various days and times. In practice, it is

difficult to detect incidents accurately using most profiling techniques; organizations should use

profiling as one of several detection and analysis techniques.

 Understand Normal Behaviors. Incident response team members should study networks, systems,

and applications to understand what their normal behavior is so that abnormal behavior can be

recognized more easily. No incident handler will have a comprehensive knowledge of all behavior

throughout the environment, but handlers should know which experts could fill in the gaps. One way

to gain this knowledge is through reviewing log entries and security alerts. This may be tedious if

filtering is not used to condense the logs to a reasonable size. As handlers become more familiar with

the logs and alerts, they should be able to focus on unexplained entries, which are usually more

important to investigate. Conducting frequent log reviews should keep the knowledge fresh, and the

analyst should be able to notice trends and changes over time. The reviews also give the analyst an

indication of the reliability of each source.

 Create a Log Retention Policy. Information regarding an incident may be recorded in several places,

such as firewall, IDPS, and application logs. Creating and implementing a log retention policy that

specifies how long log data should be maintained may be extremely helpful in analysis because older

log entries may show reconnaissance activity or previous instances of similar attacks. Another reason

for retaining logs is that incidents may not be discovered until days, weeks, or even months later. The

length of time to maintain log data is dependent on several factors, including the organization’s data

retention policies and the volume of data. See NIST SP 800-92, Guide to Computer Security Log

Management for additional recommendations related to logging.

 Perform Event Correlation. Evidence of an incident may be captured in several logs that each

contain different types of data—a firewall log may have the source IP address that was used, whereas

an application log may contain a username. A network IDPS may detect that an attack was launched

against a particular host, but it may not know if the attack was successful. The analyst may need to

examine the host’s logs to determine that information. Correlating events among multiple indicator

sources can be invaluable in validating whether a particular incident occurred.

http://csrc.nist.gov/publications/PubsSPs.html#800-92

COMPUTER SECURITY INCIDENT HANDLING GUIDE

 Keep All Host Clocks Synchronized. Protocols such as the Network Time Protocol (NTP)

synchronize clocks among hosts.

Event correlation will be more complicated if the devices reporting

events have inconsistent clock settings. From an evidentiary standpoint, it is preferable to have

consistent timestamps in logs—for example, to have three logs that show an attack occurred at

12:07:01 a.m., rather than logs that list the attack as occurring at 12:07:01, 12:10:35, and 11:07:06.

 Maintain and Use a Knowledge Base of Information. The knowledge base should include

information that handlers need for referencing quickly during incident analysis. Although it is

possible to build a knowledge base with a complex structure, a simple approach can be effective. Text

documents, spreadsheets, and relatively simple databases provide effective, flexible, and searchable

mechanisms for sharing data among team members. The knowledge base should also contain a

variety of information, including explanations of the significance and validity of precursors and

indicators, such as IDPS alerts, operating system log entries, and application error codes.

 Use Internet Search Engines for Research. Internet search engines can help analysts find

information on unusual activity. For example, an analyst may see some unusual connection attempts

targeting TCP port 22912. Performing a search on the terms “TCP,” “port,” and “22912” may return

some hits that contain logs of similar activity or even an explanation of the significance of the port

number. Note that separate workstations should be used for research to minimize the risk to the

organization from conducting these searches.

 Run Packet Sniffers to Collect Additional Data. Sometimes the indicators do not record enough

detail to permit the handler to understand what is occurring. If an incident is occurring over a

network, the fastest way to collect the necessary data may be to have a packet sniffer capture network

traffic. Configuring the sniffer to record traffic that matches specified criteria should keep the volume

of data manageable and minimize the inadvertent capture of other information. Because of privacy

concerns, some organizations may require incident handlers to request and receive permission before

using packet sniffers.

 Filter the Data. There is simply not enough time to review and analyze all the indicators; at

minimum the most suspicious activity should be investigated. One effective strategy is to filter out

categories of indicators that tend to be insignificant. Another filtering strategy is to show only the

categories of indicators that are of the highest significance; however, this approach carries substantial

risk because new malicious activity may not fall into one of the chosen indicator categories.

 Seek Assistance from Others. Occasionally, the team will be unable to determine the full cause and

nature of an incident. If the team lacks sufficient information to contain and eradicate the incident,

then it should consult with internal resources (e.g., information security staff) and external resources

(e.g., US-CERT, other CSIRTs, contractors with incident response expertise). It is important to

accurately determine the cause of each incident so that it can be fully contained and the exploited

vulnerabilities can be mitigated to prevent similar incidents from occurring.

3.2.5 Incident Documentation

An incident response team that suspects that an incident has occurred should immediately start recording

all facts regarding the incident.

A logbook is an effective and simple medium for this,

but laptops,

More information on NTP is available at http://www.ntp.org/.

Incident handlers should log only the facts regarding the incident, not personal opinions or conclusions. Subjective material

should be presented in incident reports, not recorded as evidence.

If a logbook is used, it is preferable that the logbook is bound and that the incident handlers number the pages, write in ink,

and leave the logbook intact (i.e., do not rip out any pages).

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audio recorders, and digital cameras can also serve this purpose.

Documenting system events,

conversations, and observed changes in files can lead to a more efficient, more systematic, and less error-

prone handling of the problem. Every step taken from the time the incident was detected to its final

resolution should be documented and timestamped. Every document regarding the incident should be

dated and signed by the incident handler. Information of this nature can also be used as evidence in a

court of law if legal prosecution is pursued. Whenever possible, handlers should work in teams of at least

two: one person can record and log events while the other person performs the technical tasks. Section

3.3.2 presents more information about evidence.

The incident response team should maintain records about the status of incidents, along with other

pertinent information.

Using an application or a database, such as an issue tracking system, helps ensure

that incidents are handled and resolved in a timely manner. The issue tracking system should contain

information on the following:

 The current status of the incident (new, in progress, forwarded for investigation, resolved, etc.)

 A summary of the incident

 Indicators related to the incident

 Other incidents related to this incident

 Actions taken by all incident handlers on this incident

 Chain of custody, if applicable

 Impact assessments related to the incident

 Contact information for other involved parties (e.g., system owners, system administrators)

 A list of evidence gathered during the incident investigation

 Comments from incident handlers

 Next steps to be taken (e.g., rebuild the host, upgrade an application).

The incident response team should safeguard incident data and restrict access to it because it often

contains sensitive information—for example, data on exploited vulnerabilities, recent security breaches,

and users that may have performed inappropriate actions. For example, only authorized personnel should

have access to the incident database. Incident communications (e.g., emails) and documents should be

encrypted or otherwise protected so that only authorized personnel can read them.

Consider the admissibility of evidence collected with a device before using it. For example, any devices that are potential

sources of evidence should not themselves be used to record other evidence.

NIST SP 800-86, Guide to Integrating Forensic Techniques Into Incident Response, provides detailed information on

establishing a forensic capability, including the development of policies and procedures.

Appendix B contains a suggested list of data elements to collect when incidents are reported. Also, the CERT®/CC

document State of the Practice of Computer Security Incident Response Teams (CSIRTs) provides several sample incident

reporting forms. The document is available at http://www.cert.org/archive/pdf/03tr001.pdf.

The Trans-European Research and Education Networking Association (TERENA) has developed RFC 3067, TERENA's

Incident Object Description and Exchange Format Requirements (http://www.ietf.org/rfc/rfc3067.txt). The document

provides recommendations for what information should be collected for each incident. The IETF Extended Incident

Handling (inch) Working Group (http://www.cert.org/ietf/inch/inch.html) created an RFC that expands on TERENA’s

work—RFC 5070, Incident Object Description Exchange Format (http://www.ietf.org/rfc/rfc5070.txt).

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3.2.6 Incident Prioritization

Prioritizing the handling of the incident is perhaps the most critical decision point in the incident handling

process. Incidents should not be handled on a first-come, first-served basis as a result of resource

limitations. Instead, handling should be prioritized based on the relevant factors, such as the following:

 Functional Impact of the Incident. Incidents targeting IT systems typically impact the business

functionality that those systems provide, resulting in some type of negative impact to the users of

those systems. Incident handlers should consider how the incident will impact the existing

functionality of the affected systems. Incident handlers should consider not only the current

functional impact of the incident, but also the likely future functional impact of the incident if it is not

immediately contained.

 Information Impact of the Incident. Incidents may affect the confidentiality, integrity, and

availability of the organization’s information. For example, a malicious agent may exfiltrate sensitive

information. Incident handlers should consider how this information exfiltration will impact the

organization’s overall mission. An incident that results in the exfiltration of sensitive information may

also affect other organizations if any of the data pertained to a partner organization.

 Recoverability from the Incident. The size of the incident and the type of resources it affects will

determine the amount of time and resources that must be spent on recovering from that incident. In

some instances it is not possible to recover from an incident (e.g., if the confidentiality of sensitive

information has been compromised) and it would not make sense to spend limited resources on an

elongated incident handling cycle, unless that effort was directed at ensuring that a similar incident

did not occur in the future. In other cases, an incident may require far more resources to handle than

what an organization has available. Incident handlers should consider the effort necessary to actually

recover from an incident and carefully weigh that against the value the recovery effort will create and

any requirements related to incident handling.

Combining the functional impact to the organization’s systems and the impact to the organization’s

information determines the business impact of the incident—for example, a distributed denial of service

attack against a public web server may temporarily reduce the functionality for users attempting to access

the server, whereas unauthorized root-level access to a public web server may result in the exfiltration of

personally identifiable information (PII), which could have a long-lasting impact on the organization’s

reputation.

The recoverability from the incident determines the possible responses that the team may take when

handling the incident. An incident with a high functional impact and low effort to recover from is an ideal

candidate for immediate action from the team. However, some incidents may not have smooth recovery

paths and may need to be queued for a more strategic-level response—for example, an incident that

results in an attacker exfiltrating and publicly posting gigabytes of sensitive data has no easy recovery

path since the data is already exposed; in this case the team may transfer part of the responsibility for

handling the data exfiltration incident to a more strategic-level team that develops strategy for preventing

future breaches and creates an outreach plan for alerting those individuals or organizations whose data

was exfiltrated. The team should prioritize the response to each incident based on its estimate of the

business impact caused by the incident and the estimated efforts required to recover from the incident.

An organization can best quantify the effect of its own incidents because of its situational awareness.

Table 3-2 provides examples of functional impact categories that an organization might use for rating its

own incidents. Rating incidents can be helpful in prioritizing limited resources.

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Table 3-2. Functional Impact Categories

Category

Definition

None

No effect to the organization’s ability to provide all services to all users

Low

Minimal effect; the organization can still provide all critical services to all users but has lost

efficiency

Medium

Organization has lost the ability to provide a critical service to a subset of system users

High

Organization is no longer able to provide some critical services to any users

Table 3-3 provides examples of possible information impact categories that describe the extent of

information compromise that occurred during the incident. In this table, with the exception of the ‘None’

value, the categories are not mutually exclusive and the organization could choose more than one.

Table 3-3. Information Impact Categories

Category

Definition

None

No information was exfiltrated, changed, deleted, or otherwise compromised

Privacy

Breach

Sensitive personally identifiable information (PII) of taxpayers, employees, beneficiaries, etc.

was accessed or exfiltrated

Proprietary

Breach

Unclassified proprietary information, such as protected critical infrastructure information (PCII),

was accessed or exfiltrated

Integrity

Loss

Sensitive or proprietary information was changed or deleted

Table 3-4 shows examples of recoverability effort categories that reflect the level of and type of resources

required to recover from the incident.

Table 3-4. Recoverability Effort Categories

Category

Definition

Regular

Time to recovery is predictable with existing resources

Supplemented

Time to recovery is predictable with additional resources

Extended

Time to recovery is unpredictable; additional resources and outside help are needed

Not Recoverable

Recovery from the incident is not possible (e.g., sensitive data exfiltrated and posted

publicly); launch investigation

Organizations should also establish an escalation process for those instances when the team does not

respond to an incident within the designated time. This can happen for many reasons: for example, cell

phones may fail or people may have personal emergencies. The escalation process should state how long

a person should wait for a response and what to do if no response occurs. Generally, the first step is to

duplicate the initial contact. After waiting for a brief time—perhaps 15 minutes—the caller should

escalate the incident to a higher level, such as the incident response team manager. If that person does not

respond within a certain time, then the incident should be escalated again to a higher level of

management. This process should be repeated until someone responds.

3.2.7 Incident Notification

When an incident is analyzed and prioritized, the incident response team needs to notify the appropriate

individuals so that all who need to be involved will play their roles. Incident response policies should

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include provisions concerning incident reporting—at a minimum, what must be reported to whom and at

what times (e.g., initial notification, regular status updates). The exact reporting requirements vary among

organizations, but parties that are typically notified include:

 CIO

 Head of information security

 Local information security officer

 Other incident response teams within the organization

 External incident response teams (if appropriate)

 System owner

 Human resources (for cases involving employees, such as harassment through email)

 Public affairs (for incidents that may generate publicity)

 Legal department (for incidents with potential legal ramifications)

 US-CERT (required for Federal agencies and systems operated on behalf of the Federal government;

see Section 2.3.4.3)

 Law enforcement (if appropriate)

During incident handling, the team may need to provide status updates to certain parties, even in some

cases the entire organization. The team should plan and prepare several communication methods,

including out-of-band methods (e.g., in person, paper), and select the methods that are appropriate for a

particular incident. Possible communication methods include:

 Email

 Website (internal, external, or portal)

 Telephone calls

 In person (e.g., daily briefings)

 Voice mailbox greeting (e.g., set up a separate voice mailbox for incident updates, and update the

greeting message to reflect the current incident status; use the help desk’s voice mail greeting)

 Paper (e.g., post notices on bulletin boards and doors, hand out notices at all entrance points).

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3.3 Containment, Eradication, and Recovery

Figure 3-3. Incident Response Life Cycle (Containment, Eradication, and Recovery)

3.3.1 Choosing a Containment Strategy

Containment is important before an incident overwhelms resources or increases damage. Most incidents

require containment, so that is an important consideration early in the course of handling each incident.

Containment provides time for developing a tailored remediation strategy. An essential part of

containment is decision-making (e.g., shut down a system, disconnect it from a network, disable certain

functions). Such decisions are much easier to make if there are predetermined strategies and procedures

for containing the incident. Organizations should define acceptable risks in dealing with incidents and

develop strategies accordingly.

Containment strategies vary based on the type of incident. For example, the strategy for containing an

email-borne malware infection is quite different from that of a network-based DDoS attack. Organizations

should create separate containment strategies for each major incident type, with criteria documented

clearly to facilitate decision-making. Criteria for determining the appropriate strategy include:

 Potential damage to and theft of resources

 Need for evidence preservation

 Service availability (e.g., network connectivity, services provided to external parties)

 Time and resources needed to implement the strategy

 Effectiveness of the strategy (e.g., partial containment, full containment)

 Duration of the solution (e.g., emergency workaround to be removed in four hours, temporary

workaround to be removed in two weeks, permanent solution).

In certain cases, some organizations redirect the attacker to a sandbox (a form of containment) so that

they can monitor the attacker’s activity, usually to gather additional evidence. The incident response team

should discuss this strategy with its legal department to determine if it is feasible. Ways of monitoring an

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attacker’s activity other than sandboxing should not be used; if an organization knows that a system has

been compromised and allows the compromise to continue, it may be liable if the attacker uses the

compromised system to attack other systems. The delayed containment strategy is dangerous because an

attacker could escalate unauthorized access or compromise other systems.

Another potential issue regarding containment is that some attacks may cause additional damage when

they are contained. For example, a compromised host may run a malicious process that pings another host

periodically. When the incident handler attempts to contain the incident by disconnecting the

compromised host from the network, the subsequent pings will fail. As a result of the failure, the

malicious process may overwrite or encrypt all the data on the host’s hard drive. Handlers should not

assume that just because a host has been disconnected from the network, further damage to the host has

been prevented.

3.3.2 Evidence Gathering and Handling

Although the primary reason for gathering evidence during an incident is to resolve the incident, it may

also be needed for legal proceedings.

In such cases, it is important to clearly document how all

evidence, including compromised systems, has been preserved.

Evidence should be collected according

to procedures that meet all applicable laws and regulations that have been developed from previous

discussions with legal staff and appropriate law enforcement agencies so that any evidence can be

admissible in court.

In addition, evidence should be accounted for at all times; whenever evidence is

transferred from person to person, chain of custody forms should detail the transfer and include each

party’s signature. A detailed log should be kept for all evidence, including the following:

 Identifying information (e.g., the location, serial number, model number, hostname, media access

control (MAC) addresses, and IP addresses of a computer)

 Name, title, and phone number of each individual who collected or handled the evidence during the

investigation

 Time and date (including time zone) of each occurrence of evidence handling

 Locations where the evidence was stored.

Collecting evidence from computing resources presents some challenges. It is generally desirable to

acquire evidence from a system of interest as soon as one suspects that an incident may have occurred.

Many incidents cause a dynamic chain of events to occur; an initial system snapshot may do more good in

identifying the problem and its source than most other actions that can be taken at this stage. From an

evidentiary standpoint, it is much better to get a snapshot of the system as-is rather than doing so after

incident handlers, system administrators, and others have inadvertently altered the state of the machine

during the investigation. Users and system administrators should be made aware of the steps that they

should take to preserve evidence. See NIST SP 800-86, Guide to Integrating Forensic Techniques into

Incident Response, for additional information on preserving evidence.

NIST SP 800-86, Guide to Integrating Forensic Techniques into Incident Response, provides detailed information on

establishing a forensic capability. It focuses on forensic techniques for PCs, but much of the material is applicable to other

systems. The document can be found at http://csrc.nist.gov/publications/PubsSPs.html#800-86.

Evidence gathering and handling is not typically performed for every incident that occurs—for example, most malware

incidents do not merit evidence acquisition. In many organizations, digital forensics is not needed for most incidents.

Searching and Seizing Computers and Obtaining Electronic Evidence in Criminal Investigations, from the Computer Crime

and Intellectual Property Section (CCIPS) of the Department of Justice, provides legal guidance on evidence gathering. The

document is available at http://www.cybercrime.gov/ssmanual/index.html.

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3.3.3 Identifying the Attacking Hosts

During incident handling, system owners and others sometimes want to or need to identify the attacking

host or hosts. Although this information can be important, incident handlers should generally stay focused

on containment, eradication, and recovery. Identifying an attacking host can be a time-consuming and

futile process that can prevent a team from achieving its primary goal—minimizing the business impact.

The following items describe the most commonly performed activities for attacking host identification:

 Validating the Attacking Host’s IP Address. New incident handlers often focus on the attacking

host’s IP address. The handler may attempt to validate that the address was not spoofed by verifying

connectivity to it; however, this simply indicates that a host at that address does or does not respond

to the requests. A failure to respond does not mean the address is not real—for example, a host may

be configured to ignore pings and traceroutes. Also, the attacker may have received a dynamic

address that has already been reassigned to someone else.

 Researching the Attacking Host through Search Engines. Performing an Internet search using the

apparent source IP address of an attack may lead to more information on the attack—for example, a

mailing list message regarding a similar attack.

 Using Incident Databases. Several groups collect and consolidate incident data from various

organizations into incident databases. This information sharing may take place in many forms, such

as trackers and real-time blacklists. The organization can also check its own knowledge base or issue

tracking system for related activity.

 Monitoring Possible Attacker Communication Channels. Incident handlers can monitor

communication channels that may be used by an attacking host. For example, many bots use IRC as

their primary means of communication. Also, attackers may congregate on certain IRC channels to

brag about their compromises and share information. However, incident handlers should treat any

such information that they acquire only as a potential lead, not as fact.

3.3.4 Eradication and Recovery

After an incident has been contained, eradication may be necessary to eliminate components of the

incident, such as deleting malware and disabling breached user accounts, as well as identifying and

mitigating all vulnerabilities that were exploited. During eradication, it is important to identify all affected

hosts within the organization so that they can be remediated. For some incidents, eradication is either not

necessary or is performed during recovery.

In recovery, administrators restore systems to normal operation, confirm that the systems are functioning

normally, and (if applicable) remediate vulnerabilities to prevent similar incidents. Recovery may involve

such actions as restoring systems from clean backups, rebuilding systems from scratch, replacing

compromised files with clean versions, installing patches, changing passwords, and tightening network

perimeter security (e.g., firewall rulesets, boundary router access control lists). Higher levels of system

logging or network monitoring are often part of the recovery process. Once a resource is successfully

attacked, it is often attacked again, or other resources within the organization are attacked in a similar

manner.

Eradication and recovery should be done in a phased approach so that remediation steps are prioritized.

For large-scale incidents, recovery may take months; the intent of the early phases should be to increase

the overall security with relatively quick (days to weeks) high value changes to prevent future incidents.

The later phases should focus on longer-term changes (e.g., infrastructure changes) and ongoing work to

keep the enterprise as secure as possible.

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Because eradication and recovery actions are typically OS or application-specific, detailed

recommendations and advice regarding them are outside the scope of this document.

3.4 Post-Incident Activity

Figure 3-4. Incident Response Life Cycle (Post-Incident Activity)

3.4.1 Lessons Learned

One of the most important parts of incident response is also the most often omitted: learning and

improving. Each incident response team should evolve to reflect new threats, improved technology, and

lessons learned. Holding a “lessons learned” meeting with all involved parties after a major incident, and

optionally periodically after lesser incidents as resources permit, can be extremely helpful in improving

security measures and the incident handling process itself. Multiple incidents can be covered in a single

lessons learned meeting. This meeting provides a chance to achieve closure with respect to an incident by

reviewing what occurred, what was done to intervene, and how well intervention worked. The meeting

should be held within several days of the end of the incident. Questions to be answered in the meeting

include:

 Exactly what happened, and at what times?

 How well did staff and management perform in dealing with the incident? Were the documented

procedures followed? Were they adequate?

 What information was needed sooner?

 Were any steps or actions taken that might have inhibited the recovery?

 What would the staff and management do differently the next time a similar incident occurs?

 How could information sharing with other organizations have been improved?

 What corrective actions can prevent similar incidents in the future?

 What precursors or indicators should be watched for in the future to detect similar incidents?

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 What additional tools or resources are needed to detect, analyze, and mitigate future incidents?

Small incidents need limited post-incident analysis, with the exception of incidents performed through

new attack methods that are of widespread concern and interest. After serious attacks have occurred, it is

usually worthwhile to hold post-mortem meetings that cross team and organizational boundaries to

provide a mechanism for information sharing. The primary consideration in holding such meetings is

ensuring that the right people are involved. Not only is it important to invite people who have been

involved in the incident that is being analyzed, but also it is wise to consider who should be invited for the

purpose of facilitating future cooperation.

The success of such meetings also depends on the agenda. Collecting input about expectations and needs

(including suggested topics to cover) from participants before the meeting increases the likelihood that the

participants’ needs will be met. In addition, establishing rules of order before or during the start of a

meeting can minimize confusion and discord. Having one or more moderators who are skilled in group

facilitation can yield a high payoff. Finally, it is also important to document the major points of

agreement and action items and to communicate them to parties who could not attend the meeting.

Lessons learned meetings provide other benefits. Reports from these meetings are good material for

training new team members by showing them how more experienced team members respond to incidents.

Updating incident response policies and procedures is another important part of the lessons learned

process. Post-mortem analysis of the way an incident was handled will often reveal a missing step or an

inaccuracy in a procedure, providing impetus for change. Because of the changing nature of information

technology and changes in personnel, the incident response team should review all related documentation

and procedures for handling incidents at designated intervals.

Another important post-incident activity is creating a follow-up report for each incident, which can be

quite valuable for future use. The report provides a reference that can be used to assist in handling similar

incidents. Creating a formal chronology of events (including timestamped information such as log data

from systems) is important for legal reasons, as is creating a monetary estimate of the amount of damage

the incident caused. This estimate may become the basis for subsequent prosecution activity by entities

such as the U.S. Attorney General’s office. Follow-up reports should be kept for a period of time as

specified in record retention policies.

3.4.2 Using Collected Incident Data

Lessons learned activities should produce a set of objective and subjective data regarding each incident.

Over time, the collected incident data should be useful in several capacities. The data, particularly the

total hours of involvement and the cost, may be used to justify additional funding of the incident response

team. A study of incident characteristics may indicate systemic security weaknesses and threats, as well

as changes in incident trends. This data can be put back into the risk assessment process, ultimately

leading to the selection and implementation of additional controls. Another good use of the data is

measuring the success of the incident response team. If incident data is collected and stored properly, it

should provide several measures of the success (or at least the activities) of the incident response team.

Incident data can also be collected to determine if a change to incident response capabilities causes a

corresponding change in the team’s performance (e.g., improvements in efficiency, reductions in costs).

Furthermore, organizations that are required to report incident information will need to collect the

General Records Schedule (GRS) 24, Information Technology Operations and Management Records, specifies that

“computer security incident handling, reporting and follow-up records” should be destroyed “3 years after all necessary

follow-up actions have been completed.” GRS 24 is available from the National Archives and Records Administration at

http://www.archives.gov/records-mgmt/grs/grs24.html.

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necessary data to meet their requirements. See Section 4 for additional information on sharing incident

data with other organizations.

Organizations should focus on collecting data that is actionable, rather than collecting data simply

because it is available. For example, counting the number of precursor port scans that occur each week

and producing a chart at the end of the year that shows port scans increased by eight percent is not very

helpful and may be quite time-consuming. Absolute numbers are not informative—understanding how

they represent threats to the business processes of the organization is what matters. Organizations should

decide what incident data to collect based on reporting requirements and on the expected return on

investment from the data (e.g., identifying a new threat and mitigating the related vulnerabilities before

they can be exploited.) Possible metrics for incident-related data include:

 Number of Incidents Handled.

Handling more incidents is not necessarily better—for example,

the number of incidents handled may decrease because of better network and host security controls,

not because of negligence by the incident response team. The number of incidents handled is best

taken as a measure of the relative amount of work that the incident response team had to perform, not

as a measure of the quality of the team, unless it is considered in the context of other measures that

collectively give an indication of work quality. It is more effective to produce separate incident

counts for each incident category. Subcategories also can be used to provide more information. For

example, a growing number of incidents performed by insiders could prompt stronger policy

provisions concerning background investigations for personnel and misuse of computing resources

and stronger security controls on internal networks (e.g., deploying intrusion detection software to

more internal networks and hosts).

 Time Per Incident. For each incident, time can be measured in several ways:

– Total amount of labor spent working on the incident

– Elapsed time from the beginning of the incident to incident discovery, to the initial impact

assessment, and to each stage of the incident handling process (e.g., containment, recovery)

– How long it took the incident response team to respond to the initial report of the incident

– How long it took to report the incident to management and, if necessary, appropriate external

entities (e.g., US-CERT).

 Objective Assessment of Each Incident. The response to an incident that has been resolved can be

analyzed to determine how effective it was. The following are examples of performing an objective

assessment of an incident:

– Reviewing logs, forms, reports, and other incident documentation for adherence to established

incident response policies and procedures

– Identifying which precursors and indicators of the incident were recorded to determine how

effectively the incident was logged and identified

– Determining if the incident caused damage before it was detected

Metrics such as the number of incidents handled are generally not of value in a comparison of multiple organizations

because each organization is likely to have defined key terms differently. For example, most organizations define “incident”

in terms of their own policies and practices, and what one organization considers a single incident may be considered

multiple incidents by others. More specific metrics, such as the number of port scans, are also of little value in

organizational comparisons. For example, it is highly unlikely that different security systems, such as network intrusion

detection sensors, would all use the same criteria in labeling activity as a port scan.

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– Determining if the actual cause of the incident was identified, and identifying the vector of attack,

the vulnerabilities exploited, and the characteristics of the targeted or victimized systems,

networks, and applications

– Determining if the incident is a recurrence of a previous incident

– Calculating the estimated monetary damage from the incident (e.g., information and critical

business processes negatively affected by the incident)

– Measuring the difference between the initial impact assessment and the final impact assessment

(see Section 3.2.6)

– Identifying which measures, if any, could have prevented the incident.

 Subjective Assessment of Each Incident. Incident response team members may be asked to assess

their own performance, as well as that of other team members and of the entire team. Another

valuable source of input is the owner of a resource that was attacked, in order to determine if the

owner thinks the incident was handled efficiently and if the outcome was satisfactory.

Besides using these metrics to measure the team’s success, organizations may also find it useful to

periodically audit their incident response programs. Audits will identify problems and deficiencies that

can then be corrected. At a minimum, an incident response audit should evaluate the following items

against applicable regulations, policies, and generally accepted practices:

 Incident response policies, plans, and procedures

 Tools and resources

 Team model and structure

 Incident handler training and education

 Incident documentation and reports

 The measures of success discussed earlier in this section.

3.4.3 Evidence Retention

Organizations should establish policy for how long evidence from an incident should be retained. Most

organizations choose to retain all evidence for months or years after the incident ends. The following

factors should be considered during the policy creation:

 Prosecution. If it is possible that the attacker will be prosecuted, evidence may need to be retained

until all legal actions have been completed. In some cases, this may take several years. Furthermore,

evidence that seems insignificant now may become more important in the future. For example, if an

attacker is able to use knowledge gathered in one attack to perform a more severe attack later,

evidence from the first attack may be key to explaining how the second attack was accomplished.

 Data Retention. Most organizations have data retention policies that state how long certain types of

data may be kept. For example, an organization may state that email messages should be retained for

only 180 days. If a disk image contains thousands of emails, the organization may not want the image

to be kept for more than 180 days unless it is absolutely necessary. As discussed in Section 3.4.2,

General Records Schedule (GRS) 24 specifies that incident handling records should be kept for

three years.

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 Cost. Original hardware (e.g., hard drives, compromised systems) that is stored as evidence, as well

as hard drives and removable media that are used to hold disk images, are generally individually

inexpensive. However, if an organization stores many such components for years, the cost can be

substantial. The organization also must retain functional computers that can use the stored hardware

and media.

3.5 Incident Handling Checklist

The checklist in Table 3-6 provides the major steps to be performed in the handling of an incident. Note

that the actual steps performed may vary based on the type of incident and the nature of individual

incidents. For example, if the handler knows exactly what has happened based on analysis of indicators

(Step 1.1), there may be no need to perform Steps 1.2 or 1.3 to further research the activity. The checklist

provides guidelines to handlers on the major steps that should be performed; it does not dictate the exact

sequence of steps that should always be followed.

Table 3-5. Incident Handling Checklist

Action

Completed

Detection and Analysis

Determine whether an incident has occurred

1.1

Analyze the precursors and indicators

1.2

Look for correlating information

1.3

Perform research (e.g., search engines, knowledge base)

1.4

As soon as the handler believes an incident has occurred, begin documenting

the investigation and gathering evidence

Prioritize handling the incident based on the relevant factors (functional impact, information

impact, recoverability effort, etc.)

Report the incident to the appropriate internal personnel and external organizations

Containment, Eradication, and Recovery

Acquire, preserve, secure, and document evidence

Contain the incident

Eradicate the incident

6.1

Identify and mitigate all vulnerabilities that were exploited

6.2

Remove malware, inappropriate materials, and other components

6.3

If more affected hosts are discovered (e.g., new malware infections), repeat

the Detection and Analysis steps (1.1, 1.2) to identify all other affected hosts, then

contain (5) and eradicate (6) the incident for them

Recover from the incident

7.1

Return affected systems to an operationally ready state

7.2

Confirm that the affected systems are functioning normally

7.3

If necessary, implement additional monitoring to look for future related activity

Post-Incident Activity

Create a follow-up report

Hold a lessons learned meeting (mandatory for major incidents, optional otherwise)

3.6 Recommendations

The key recommendations presented in this section for handling incidents are summarized below.

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 Acquire tools and resources that may be of value during incident handling. The team will be

more efficient at handling incidents if various tools and resources are already available to them.

Examples include contact lists, encryption software, network diagrams, backup devices, digital

forensic software, and port lists.

 Prevent incidents from occurring by ensuring that networks, systems, and applications are

sufficiently secure. Preventing incidents is beneficial to the organization and also reduces the

workload of the incident response team. Performing periodic risk assessments and reducing the

identified risks to an acceptable level are effective in reducing the number of incidents. Awareness of

security policies and procedures by users, IT staff, and management is also very important.

 Identify precursors and indicators through alerts generated by several types of security

software. Intrusion detection and prevention systems, antivirus software, and file integrity checking

software are valuable for detecting signs of incidents. Each type of software may detect incidents that

the other types of software cannot, so the use of several types of computer security software is highly

recommended. Third-party monitoring services can also be helpful.

 Establish mechanisms for outside parties to report incidents. Outside parties may want to report

incidents to the organization—for example, they may believe that one of the organization’s users is

attacking them. Organizations should publish a phone number and email address that outside parties

can use to report such incidents.

 Require a baseline level of logging and auditing on all systems, and a higher baseline level on all

critical systems. Logs from operating systems, services, and applications frequently provide value

during incident analysis, particularly if auditing was enabled. The logs can provide information such

as which accounts were accessed and what actions were performed.

 Profile networks and systems. Profiling measures the characteristics of expected activity levels so

that changes in patterns can be more easily identified. If the profiling process is automated, deviations

from expected activity levels can be detected and reported to administrators quickly, leading to faster

detection of incidents and operational issues.

 Understand the normal behaviors of networks, systems, and applications. Team members who

understand normal behavior should be able to recognize abnormal behavior more easily. This

knowledge can best be gained by reviewing log entries and security alerts; the handlers should

become familiar with the typical data and can investigate the unusual entries to gain more knowledge.

 Create a log retention policy. Information regarding an incident may be recorded in several places.

Creating and implementing a log retention policy that specifies how long log data should be

maintained may be extremely helpful in analysis because older log entries may show reconnaissance

activity or previous instances of similar attacks.

 Perform event correlation. Evidence of an incident may be captured in several logs. Correlating

events among multiple sources can be invaluable in collecting all the available information for an

incident and validating whether the incident occurred.

 Keep all host clocks synchronized. If the devices reporting events have inconsistent clock settings,

event correlation will be more complicated. Clock discrepancies may also cause issues from an

evidentiary standpoint.

 Maintain and use a knowledge base of information. Handlers need to reference information

quickly during incident analysis; a centralized knowledge base provides a consistent, maintainable

source of information. The knowledge base should include general information, such as data on

precursors and indicators of previous incidents.

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 Start recording all information as soon as the team suspects that an incident has occurred.

Every step taken, from the time the incident was detected to its final resolution, should be

documented and timestamped. Information of this nature can serve as evidence in a court of law if

legal prosecution is pursued. Recording the steps performed can also lead to a more efficient,

systematic, and less error-prone handling of the problem.

 Safeguard incident data. It often contains sensitive information regarding such things as

vulnerabilities, security breaches, and users that may have performed inappropriate actions. The team

should ensure that access to incident data is restricted properly, both logically and physically.

 Prioritize handling of the incidents based on the relevant factors. Because of resource limitations,

incidents should not be handled on a first-come, first-served basis. Instead, organizations should

establish written guidelines that outline how quickly the team must respond to the incident and what

actions should be performed, based on relevant factors such as the functional and information impact

of the incident, and the likely recoverability from the incident. This saves time for the incident

handlers and provides a justification to management and system owners for their actions.

Organizations should also establish an escalation process for those instances when the team does not

respond to an incident within the designated time.

 Include provisions regarding incident reporting in the organization’s incident response policy.

Organizations should specify which incidents must be reported, when they must be reported, and to

whom. The parties most commonly notified are the CIO, head of information security, local

information security officer, other incident response teams within the organization, and system

owners.

 Establish strategies and procedures for containing incidents. It is important to contain incidents

quickly and effectively to limit their business impact. Organizations should define acceptable risks in

containing incidents and develop strategies and procedures accordingly. Containment strategies

should vary based on the type of incident.

 Follow established procedures for evidence gathering and handling. The team should clearly

document how all evidence has been preserved. Evidence should be accounted for at all times. The

team should meet with legal staff and law enforcement agencies to discuss evidence handling, then

develop procedures based on those discussions.

 Capture volatile data from systems as evidence. This includes lists of network connections,

processes, login sessions, open files, network interface configurations, and the contents of memory.

Running carefully chosen commands from trusted media can collect the necessary information

without damaging the system’s evidence.

 Obtain system snapshots through full forensic disk images, not file system backups. Disk images

should be made to sanitized write-protectable or write-once media. This process is superior to a file

system backup for investigatory and evidentiary purposes. Imaging is also valuable in that it is much

safer to analyze an image than it is to perform analysis on the original system because the analysis

may inadvertently alter the original.

 Hold lessons learned meetings after major incidents. Lessons learned meetings are extremely

helpful in improving security measures and the incident handling process itself.

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4. Coordination and Information Sharing

The nature of contemporary threats and attacks makes it more important than ever for organizations to

work together during incident response. Organizations should ensure that they effectively coordinate

portions of their incident response activities with appropriate partners. The most important aspect of

incident response coordination is information sharing, where different organizations share threat, attack,

and vulnerability information with each other so that each organization’s knowledge benefits the other.

Incident information sharing is frequently mutually beneficial because the same threats and attacks often

affect multiple organizations simultaneously.

As mentioned in Section 2, coordinating and sharing information with partner organizations can

strengthen the organization’s ability to effectively respond to IT incidents. For example, if an organization

identifies some behavior on its network that seems suspicious and sends information about the event to a

set of trusted partners, someone else in that network may have already seen similar behavior and be able

to respond with additional details about the suspicious activity, including signatures, other indicators to

look for, or suggested remediation actions. Collaboration with the trusted partner can enable an

organization to respond to the incident more quickly and efficiently than an organization operating in

isolation.

This increase in efficiency for standard incident response techniques is not the only incentive for cross-

organization coordination and information sharing. Another incentive for information sharing is the

ability to respond to incidents using techniques that may not be available to a single organization,

especially if that organization is small to medium size. For example, a small organization that identifies a

particularly complex instance of malware on its network may not have the in-house resources to fully

analyze the malware and determine its effect on the system. In this case, the organization may be able to

leverage a trusted information sharing network to effectively outsource the analysis of this malware to

third party resources that have the adequate technical capabilities to perform the malware analysis.

This section of the document highlights coordination and information sharing. Section 4.1 presents an

overview of incident response coordination and focuses on the need for cross-organization coordination to

supplement organization incident response processes. Section 4.2 discusses techniques for information

sharing across organizations, and Section 4.3 examines how to restrict what information is shared or not

shared with other organizations.

4.1 Coordination

As discussed in Section 2.3.4, an organization may need to interact with several types of external

organizations in the course of conducting incident response activities. Examples of these organizations

include other incident response teams, law enforcement agencies, Internet service providers, and

constituents and customers. An organization’s incident response team should plan its incident

coordination with those parties before incidents occur to ensure that all parties know their roles and that

effective lines of communication are established. Figure 4-1 provides a sample view into an organization

performing coordination at every phase of the incident response lifecycle, highlighting that coordination

is valuable throughout the lifecycle.

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Figure 4-1. Incident Response Coordination

4.1.1 Coordination Relationships

An incident response team within an organization may participate in different types of coordination

arrangements, depending on the type of organization with which it is coordinating. For example, the team

members responsible for the technical details of incident response may coordinate with operational

colleagues at partner organizations to share strategies for mitigating an attack spanning multiple

organizations. Alternatively, during the same incident, the incident response team manager may

coordinate with ISACs to satisfy necessary reporting requirements and seek advice and additional

resources for successfully responding to the incident. Table 4-1 provides some examples of coordination

relationships that may exist when collaborating with outside organizations.

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Table 4-1. Coordination Relationships

Category

Definition

Information Shared

Team-to-

team

Team-to-team relationships exist whenever

technical incident responders in different

organizations collaborate with their peers

during any phase of the incident handling life

cycle. The organizations participating in this

type of relationship are usually peers without

any authority over each other and choose to

share information, pool resources, and reuse

knowledge to solve problems common to both

teams.

The information most frequently shared in team-to-

team relationships is tactical and technical (e.g.,

technical indicators of compromise, suggested

remediation actions) but may also include other

types of information (plans, procedures, lessons

learned) if conducted as part of the Preparation

phase.

Team-to-

coordinating

team

Team-to-coordinating team relationships exist

between an organizational incident response

team and a separate organization that acts as

a central point for coordinated incident

response and management such as US-

CERT or an ISAC. This type of relationship

may include some degree of required

reporting from the member organizations by

the coordinating body, as well as the

expectation that the coordinating team will

disseminate timely and useful information to

participating member organizations.

Teams and coordinating teams frequently share

tactical, technical information as well as information

regarding threats, vulnerabilities, and risks to the

community served by the coordinating team. The

coordinating team may also need specific impact

information about incidents in order to help make

decisions on where to focus its resources and

attention.

Coordinating

team-to-

coordinating

team

Relationships between multiple coordinating

teams such as US-CERT and the ISACs exist

to share information relating to cross-cutting

incidents which may affect multiple

communities. The coordinating teams act on

behalf of their respective community member

organizations to share information on the

nature and scope of cross-cutting incidents

and reusable mitigation strategies to assist in

inter-community response.

The type of information shared by coordinating

teams with their counterparts often consists of

periodical summaries during “steady state”

operations, punctuated by the exchange of tactical,

technical details, response plans, and impact or risk

assessment information during coordinated incident

response activities.

Organizations may find it challenging to build the relationships needed for coordination. Good places to

start building a community include the industry sector that the organization belongs to and the geographic

region where the organization operates. An organization’s incident response team can try to form

relationships with other teams (at the team-to-team level) within its own industry sector and region, or

join established bodies within the industry sector that already facilitate information sharing. Another

consideration for building relationships is that some relationships are mandatory and others voluntary; for

example, team-to-coordinating team relationships are often mandatory, while team-to-team relationships

are usually voluntary. Organizations pursue voluntary relationships because they fulfill mutual self-

interests. Mandatory relationships are usually defined by a regulatory body within the industry or by

another entity.

4.1.2 Sharing Agreements and Reporting Requirements

Organizations trying to share information with external organizations should consult with their legal

department before initiating any coordination efforts. There may be contracts or other agreements that

need to be put into place before discussions occur. An example is a nondisclosure agreement (NDA) to

protect the confidentiality of the organization’s most sensitive information. Organizations should also

consider any existing requirements for reporting, such as sharing incident information with an ISAC or

reporting incidents to a higher-level CIRT.

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4.2 Information Sharing Techniques

Information sharing is a key element of enabling coordination across organizations. Even the smallest

organizations need to be able to share incident information with peers and partners in order to deal with

many incidents effectively. Organizations should perform such information sharing throughout the

incident response life cycle and not wait until an incident has been fully resolved before sharing details of

it with others. Section 4.3 discusses the types of incident information that organizations may or may not

want to share with others.

This section focuses on techniques for information sharing. Section 4.2.1 looks at ad hoc methods, while

Section 4.2.2 examines partially automated methods. Finally, Section 4.2.3 discusses security

considerations related to information sharing.

4.2.1 Ad Hoc

Most incident information sharing has traditionally occurred through ad hoc methods, such as email,

instant messaging clients, and phone. Ad hoc information sharing mechanisms normally rely on an

individual employee’s connections with employees in incident response teams of partner organizations.

The employee uses these connections to manually share information with peers and coordinate with them

to construct strategies for responding to an incident. Depending on the size of the organization, these ad

hoc techniques may be the most cost-effective way of sharing information with partner organizations.

However, due to the informal nature of ad hoc information sharing, it is not possible to guarantee that the

information sharing processes will always operate. For example, if a particularly well-connected

employee resigns from an incident response team, that team may temporarily lose the majority of

information sharing channels it relies on to effectively coordinate with outside organizations.

Ad hoc information sharing methods are also largely unstandardized in terms of what information is

communicated and how that communication occurs. Because of the lack of standardization, they tend to

require manual intervention and to be more resource-intensive to process than the alternative, partially

automated methods. Whenever possible an organization should attempt to formalize its information

sharing strategies through formal agreements with partner organizations and technical mechanisms that

will help to partially automate the sharing of information.

4.2.2 Partially Automated

Organizations should attempt to automate as much of the information sharing process as possible to make

cross-organizational coordination efficient and cost effective. In reality, it will not be possible to fully

automate the sharing of all incident information, nor will it be desirable due to security and trust

considerations. Organizations should attempt to achieve a balance of automated information sharing

overlaid with human-centric processes for managing the information flow.

When engineering automated information sharing solutions, organizations should first consider what

types of information they will communicate with partners. The organization may want to construct a

formal data dictionary enumerating all entities and relationships between entities that they will wish to

share. Once the organization understands the types of information they will share, it is necessary to

construct formal, machine-processable models to capture this information. Wherever possible, an

organization should use existing data exchange standards for representing the information they need to

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share.

The organization should work with its partner organizations when deciding on the data exchange

models to ensure that the standards selected are compatible with the partner organization’s incident

response systems. When selecting existing data exchange models, organizations may prefer to select

multiple models that model different aspects of the incident response domain and then leverage these

models in a modular fashion, communicating only the information needed at a specific decision point in

the life cycle. Appendix E provides a non-exhaustive list of existing standards defining data exchange

models that are applicable to the incident response domain.

In addition to selecting the data exchange models for sharing incident information, an organization must

also work with its partner organizations to agree on the technical transport mechanisms for enabling the

information exchange to occur in an automated fashion. These transport mechanisms include, at a

minimum, the transport protocol for exchanging the information, the architectural model for

communicating with an information resource, and the applicable ports and domain names for accessing an

information resource in a particular organization. For example, a group of partner organizations may

decide to exchange incident information using a Representational State Transfer (REST) architecture to

exchange IODEF/Real-Time Inter-Network Defense (RID) data over Hypertext Transfer Protocol Secure

(HTTPS) on port 4590 of a specific domain name within each organization’s DMZ.

4.2.3 Security Considerations

There are several security considerations that incident response teams should consider when planning

their information sharing. One is being able to designate who can see which pieces of incident

information (e.g., protection of sensitive information). It may also be necessary to perform data

sanitization or scrubbing to remove sensitive pieces of data from the incident information without

disturbing the information on precursors, indicators, and other technical information. See Section 4.3 for

more information on granular information sharing. The incident response team should also ensure that the

necessary measures are taken to protect information shared with the team by other organizations.

There are also many legal issues to consider regarding data sharing. See Section 4.1.2 for additional

information.

4.3 Granular Information Sharing

Organizations need to balance the benefits of information sharing with the drawbacks of sharing sensitive

information, ideally sharing the necessary information and only the necessary information with the

appropriate parties. Organizations can think of their incident information as being comprised of two types

of information: business impact and technical. Business impact information is often shared in the context

of a team-to-coordinating-team relationship as defined in Section 4.1.1, while technical information is

often shared within all three types of coordination relationships. This section discusses both types of

information and provides recommendations for performing granular information sharing.

4.3.1 Business Impact Information

Business impact information involves how the incident is affecting the organization in terms of mission

impact, financial impact, etc. Such information, at least at a summary level, is often reported to higher-

level coordinating incident response teams to communicate an estimate of the damage caused by the

incident. Coordinating response teams may need this impact information to make decisions regarding the

According to the National Technology Transfer and Advancement Act (NTTAA), “all Federal agencies and departments

shall use technical standards that are developed or adopted by voluntary consensus standards bodies”. See

http://standards.gov/nttaa.cfm for more details.

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degree of assistance to provide to the reporting organization. A coordinating team may also use this

information to make decisions relative to how a specific incident will affect other organizations in the

community they represent.

Coordinating teams may require member organizations to report on some degree of business impact

information. For example, a coordinating team may require a member organization to report impact

information using the categories defined in Section 3.2.6. In this case, for a hypothetical incident an

organization would report that it has a functional impact of medium, an information impact of none, and

will require extended recoverability time. This high-level information would alert the coordinating team

that the member organization requires some level of additional resources to recover from the incident.

The coordinating team could then pursue additional communication with the member organization to

determine how many resources are required as well as the type of resources based on the technical

information provided about the incident.

Business impact information is only useful for reporting to organizations that have some interest in

ensuring the mission of the organization experiencing the incident. In many cases, incident response

teams should avoid sharing business impact information with outside organizations unless there is a clear

value proposition or formal reporting requirements. When sharing information with peer and partner

organizations, incident response teams should focus on exchanging technical information as outlined in

Section 4.3.2.

4.3.2 Technical Information

There are many different types of technical indicators signifying the occurrence of an incident within an

organization. These indicators originate from the variety of technical information associated with

incidents, such as the hostnames and IP addresses of attacking hosts, samples of malware, precursors and

indicators of similar incidents, and types of vulnerabilities exploited in an incident. Section 3.2.2 provides

an overview of how organizations should collect and utilize these indicators to help identify an incident

that is in progress. In addition, Section 3.2.3 provides a listing of common sources of incident indicator

data.

While organizations gain value from collecting their own internal indicators, they may gain additional

value from analyzing indicators received from partner organizations and sharing internal indicators for

external analysis and use. If the organization receives external indicator data pertaining to an incident they

have not seen, they can use that indicator data to identify the incident as it begins to occur. Similarly, an

organization may use external indicator data to detect an ongoing incident that it was not aware of due to

the lack of internal resources to capture the specific indicator data. Organizations may also benefit from

sharing their internal indicator data with external organizations. For example, if they share technical

information pertaining to an incident they are experiencing, a partner organization may respond with a

suggested remediation strategy for handling that incident.

Organizations should share as much of this information as possible; however, there may be both security

and liability reasons why an organization would not want to reveal the details of an exploited

vulnerability. External indicators, such as the general characteristics of attacks and the identity of

attacking hosts, are usually safe to share with others. Organizations should consider which types of

technical information should or should not be shared with various parties, and then endeavor to share as

much of the appropriate information as possible with other organizations.

Technical indicator data is useful when it allows an organization to identify an actual incident. However,

not all indicator data received from external sources will pertain to the organization receiving it. In some

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cases, this external data will generate false positives within the receiving organization's network and may

cause resources to be spent on nonexistent problems.

Organizations participating in incident information sharing should have staff skilled in taking technical

indicator information from sharing communities and disseminating that information throughout the

enterprise, preferably in an automated way. Organizations should also attempt to ensure that they only

share an indicator for which they have a relatively high level of confidence that it signifies an actual

incident.

4.4 Recommendations

The key recommendations presented in this section for handling incidents are summarized below.

 Plan incident coordination with external parties before incidents occur. Examples of external

parties include other incident response teams, law enforcement agencies, Internet service providers,

and constituents and customers. This planning helps ensure that all parties know their roles and that

effective lines of communication are established.

 Consult with the legal department before initiating any coordination efforts. There may be

contracts or other agreements that need to be put into place before discussions occur.

 Perform incident information sharing throughout the incident response life cycle. Information

sharing is a key element of enabling coordination across organizations. Organizations should not wait

until an incident has been fully resolved before sharing details of it with others.

 Attempt to automate as much of the information sharing process as possible. This makes cross-

organizational coordination efficient and cost effective. Organizations should attempt to achieve a

balance of automated information sharing overlaid with human-centric processes for managing the

information flow.

 Balance the benefits of information sharing with the drawbacks of sharing sensitive

information. Ideally organizations should share the necessary information and only the necessary

information with the appropriate parties. Business impact information is often shared in a team-to-

coordinating team relationship, while technical information is often shared within all types of

coordination relationships. When sharing information with peer and partner organizations, incident

response teams should focus on exchanging technical information.

 Share as much of the appropriate incident information as possible with other organizations.

Organizations should consider which types of technical information should or should not be shared

with various parties. For example, external indicators, such as the general characteristics of attacks

and the identity of attacking hosts, are usually safe to share with others, but there may be both

security and liability reasons why an organization would not want to reveal the details of an exploited

vulnerability.

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Appendix A—Incident Handling Scenarios

Incident handling scenarios provide an inexpensive and effective way to build incident response skills and

identify potential issues with incident response processes. The incident response team or team members

are presented with a scenario and a list of related questions. The team then discusses each question and

determines the most likely answer. The goal is to determine what the team would really do and to

compare that with policies, procedures, and generally recommended practices to identify discrepancies or

deficiencies. For example, the answer to one question may indicate that the response would be delayed

because the team lacks a piece of software or because another team does not provide off-hours support.

The questions listed below are applicable to almost any scenario. Each question is followed by a reference

to the related section(s) of the document. After the questions are scenarios, each of which is followed by

additional incident-specific questions. Organizations are strongly encouraged to adapt these questions and

scenarios for use in their own incident response exercises.

A.1 Scenario Questions

Preparation:

1. Would the organization consider this activity to be an incident? If so, which of the organization’s

policies does this activity violate? (Section 2.1)

2. What measures are in place to attempt to prevent this type of incident from occurring or to limit

its impact? (Section 3.1.2)

Detection and Analysis:

1. What precursors of the incident, if any, might the organization detect? Would any precursors

cause the organization to take action before the incident occurred? (Sections 3.2.2, 3.2.3)

2. What indicators of the incident might the organization detect? Which indicators would cause

someone to think that an incident might have occurred? (Sections 3.2.2, 3.2.3)

3. What additional tools might be needed to detect this particular incident? (Section 3.2.3)

4. How would the incident response team analyze and validate this incident? What personnel would

be involved in the analysis and validation process? (Section 3.2.4)

5. To which people and groups within the organization would the team report the incident? (Section

3.2.7)

6. How would the team prioritize the handling of this incident? (Section 3.2.6)

Containment, Eradication, and Recovery:

1. What strategy should the organization take to contain the incident? Why is this strategy preferable

to others? (Section 3.3.1)

2. What could happen if the incident were not contained? (Section 3.3.1)

3. What additional tools might be needed to respond to this particular incident? (Sections 3.3.1,

3.3.4)

4. Which personnel would be involved in the containment, eradication, and/or recovery processes?

(Sections 3.3.1, 3.3.4)

For additional information on exercises, see NIST SP 800-84, Guide to Test, Training, and Exercise Programs for IT Plans

and Capabilities, which is available at http://csrc.nist.gov/publications/PubsSPs.html#800-84.

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5. What sources of evidence, if any, should the organization acquire? How would the evidence be

acquired? Where would it be stored? How long should it be retained? (Sections 3.2.5, 3.3.2, 3.4.3)

Post-Incident Activity:

1. Who would attend the lessons learned meeting regarding this incident? (Section 3.4.1)

2. What could be done to prevent similar incidents from occurring in the future? (Section 3.1.2)

3. What could be done to improve detection of similar incidents? (Section 3.1.2)

General Questions:

1. How many incident response team members would participate in handling this incident? (Section

2.4.3)

2. Besides the incident response team, what groups within the organization would be involved in

handling this incident? (Section 2.4.4)

3. To which external parties would the team report the incident? When would each report occur?

How would each report be made? What information would you report or not report, and why?

(Section 2.3.2)

4. What other communications with external parties may occur? (Section 2.3.2)

5. What tools and resources would the team use in handling this incident? (Section 3.1.1)

6. What aspects of the handling would have been different if the incident had occurred at a different

day and time (on-hours versus off-hours)? (Section 2.4.2)

7. What aspects of the handling would have been different if the incident had occurred at a different

physical location (onsite versus offsite)? (Section 2.4.2)

A.2 Scenarios

Scenario 1: Domain Name System (DNS) Server Denial of Service (DoS)

On a Saturday afternoon, external users start having problems accessing the organization’s public

websites. Over the next hour, the problem worsens to the point where nearly every access attempt fails.

Meanwhile, a member of the organization’s networking staff responds to alerts from an Internet border

router and determines that the organization’s Internet bandwidth is being consumed by an unusually large

volume of User Datagram Protocol (UDP) packets to and from both the organization’s public DNS

servers. Analysis of the traffic shows that the DNS servers are receiving high volumes of requests from a

single external IP address. Also, all the DNS requests from that address come from the same source port.

The following are additional questions for this scenario:

1. Whom should the organization contact regarding the external IP address in question?

2. Suppose that after the initial containment measures were put in place, the network administrators

detected that nine internal hosts were also attempting the same unusual requests to the DNS

server. How would that affect the handling of this incident?

3. Suppose that two of the nine internal hosts disconnected from the network before their system

owners were identified. How would the system owners be identified?

Scenario 2: Worm and Distributed Denial of Service (DDoS) Agent Infestation

On a Tuesday morning, a new worm is released; it spreads itself through removable media, and it can

copy itself to open Windows shares. When the worm infects a host, it installs a DDoS agent. The

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organization has already incurred widespread infections before antivirus signatures become available

several hours after the worm started to spread.

The following are additional questions for this scenario:

1. How would the incident response team identify all infected hosts?

2. How would the organization attempt to prevent the worm from entering the organization before

antivirus signatures were released?

3. How would the organization attempt to prevent the worm from being spread by infected hosts

before antivirus signatures were released?

4. Would the organization attempt to patch all vulnerable machines? If so, how would this be done?

5. How would the handling of this incident change if infected hosts that had received the DDoS

agent had been configured to attack another organization’s website the next morning?

6. How would the handling of this incident change if one or more of the infected hosts contained

sensitive personally identifiable information regarding the organization’s employees?

7. How would the incident response team keep the organization’s users informed about the status of

the incident?

8. What additional measures would the team perform for hosts that are not currently connected to

the network (e.g., staff members on vacation, offsite employees who connect occasionally)?

Scenario 3: Stolen Documents

On a Monday morning, the organization’s legal department receives a call from the Federal Bureau of

Investigation (FBI) regarding some suspicious activity involving the organization’s systems. Later that

day, an FBI agent meets with members of management and the legal department to discuss the activity.

The FBI has been investigating activity involving public posting of sensitive government documents, and

some of the documents reportedly belong to the organization. The agent asks for the organization’s

assistance, and management asks for the incident response team’s assistance in acquiring the necessary

evidence to determine if these documents are legitimate or not and how they might have been leaked.

The following are additional questions for this scenario:

1. From what sources might the incident response team gather evidence?

2. What would the team do to keep the investigation confidential?

3. How would the handling of this incident change if the team identified an internal host responsible

for the leaks?

4. How would the handling of this incident change if the team found a rootkit installed on the

internal host responsible for the leaks?

Scenario 4: Compromised Database Server

On a Tuesday night, a database administrator performs some off-hours maintenance on several production

database servers. The administrator notices some unfamiliar and unusual directory names on one of the

servers. After reviewing the directory listings and viewing some of the files, the administrator concludes

that the server has been attacked and calls the incident response team for assistance. The team’s

investigation determines that the attacker successfully gained root access to the server six weeks ago.

The following are additional questions for this scenario:

1. What sources might the team use to determine when the compromise had occurred?

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2. How would the handling of this incident change if the team found that the database server had

been running a packet sniffer and capturing passwords from the network?

3. How would the handling of this incident change if the team found that the server was running a

process that would copy a database containing sensitive customer information (including

personally identifiable information) each night and transfer it to an external address?

4. How would the handling of this incident change if the team discovered a rootkit on the server?

Scenario 5: Unknown Exfiltration

On a Sunday night, one of the organization’s network intrusion detection sensors alerts on anomalous

outbound network activity involving large file transfers. The intrusion analyst reviews the alerts; it

appears that thousands of .RAR files are being copied from an internal host to an external host, and the

external host is located in another country. The analyst contacts the incident response team so that it can

investigate the activity further. The team is unable to see what the .RAR files hold because their contents

are encrypted. Analysis of the internal host containing the .RAR files shows signs of a bot installation.

The following are additional questions for this scenario:

1. How would the team determine what was most likely inside the .RAR files? Which other teams

might assist the incident response team?

2. If the incident response team determined that the initial compromise had been performed through

a wireless network card in the internal host, how would the team further investigate this activity?

3. If the incident response team determined that the internal host was being used to stage sensitive

files from other hosts within the enterprise, how would the team further investigate this activity?

Scenario 6: Unauthorized Access to Payroll Records

On a Wednesday evening, the organization’s physical security team receives a call from a payroll

administrator who saw an unknown person leave her office, run down the hallway, and exit the building.

The administrator had left her workstation unlocked and unattended for only a few minutes. The payroll

program is still logged in and on the main menu, as it was when she left it, but the administrator notices

that the mouse appears to have been moved. The incident response team has been asked to acquire

evidence related to the incident and to determine what actions were performed.

The following are additional questions for this scenario:

1. How would the team determine what actions had been performed?

2. How would the handling of this incident differ if the payroll administrator had recognized the

person leaving her office as a former payroll department employee?

3. How would the handling of this incident differ if the team had reason to believe that the person

was a current employee?

4. How would the handling of this incident differ if the physical security team determined that the

person had used social engineering techniques to gain physical access to the building?

5. How would the handling of this incident differ if logs from the previous week showed an

unusually large number of failed remote login attempts using the payroll administrator’s user ID?

6. How would the handling of this incident differ if the incident response team discovered that a

keystroke logger was installed on the computer two weeks earlier?

COMPUTER SECURITY INCIDENT HANDLING GUIDE

Scenario 7: Disappearing Host

On a Thursday afternoon, a network intrusion detection sensor records vulnerability scanning activity

directed at internal hosts that is being generated by an internal IP address. Because the intrusion detection

analyst is unaware of any authorized, scheduled vulnerability scanning activity, she reports the activity to

the incident response team. When the team begins the analysis, it discovers that the activity has stopped

and that there is no longer a host using the IP address.

The following are additional questions for this scenario:

1. What data sources might contain information regarding the identity of the vulnerability scanning

host?

2. How would the team identify who had been performing the vulnerability scans?

3. How would the handling of this incident differ if the vulnerability scanning were directed at the

organization’s most critical hosts?

4. How would the handling of this incident differ if the vulnerability scanning were directed at

external hosts?

5. How would the handling of this incident differ if the internal IP address was associated with the

organization’s wireless guest network?

6. How would the handling of this incident differ if the physical security staff discovered that

someone had broken into the facility half an hour before the vulnerability scanning occurred?

Scenario 8: Telecommuting Compromise

On a Saturday night, network intrusion detection software records an inbound connection originating

from a watchlist IP address. The intrusion detection analyst determines that the connection is being made

to the organization’s VPN server and contacts the incident response team. The team reviews the intrusion

detection, firewall, and VPN server logs and identifies the user ID that was authenticated for the session

and the name of the user associated with the user ID.

The following are additional questions for this scenario:

1. What should the team’s next step be (e.g., calling the user at home, disabling the user ID,

disconnecting the VPN session)? Why should this step be performed first? What step should be

performed second?

2. How would the handling of this incident differ if the external IP address belonged to an open

proxy?

3. How would the handling of this incident differ if the ID had been used to initiate VPN

connections from several external IP addresses without the knowledge of the user?

4. Suppose that the identified user’s computer had become compromised by a game containing a

Trojan horse that was downloaded by a family member. How would this affect the team’s

analysis of the incident? How would this affect evidence gathering and handling? What should

the team do in terms of eradicating the incident from the user’s computer?

5. Suppose that the user installed antivirus software and determined that the Trojan horse had

included a keystroke logger. How would this affect the handling of the incident? How would this

affect the handling of the incident if the user were a system administrator? How would this affect

the handling of the incident if the user were a high-ranking executive in the organization?

COMPUTER SECURITY INCIDENT HANDLING GUIDE

Scenario 9: Anonymous Threat

On a Thursday afternoon, the organization’s physical security team receives a call from an IT manager,

reporting that two of her employees just received anonymous threats against the organization’s systems.

Based on an investigation, the physical security team believes that the threats should be taken seriously

and notifies the appropriate internal teams, including the incident response team, of the threats.

The following are additional questions for this scenario:

1. What should the incident response team do differently, if anything, in response to the notification

of the threats?

2. What impact could heightened physical security controls have on the team’s responses to

incidents?

Scenario 10: Peer-to-Peer File Sharing

The organization prohibits the use of peer-to-peer file sharing services. The organization’s network

intrusion detection sensors have signatures enabled that can detect the usage of several popular peer-to-

peer file sharing services. On a Monday evening, an intrusion detection analyst notices that several file

sharing alerts have occurred during the past three hours, all involving the same internal IP address.

1. What factors should be used to prioritize the handling of this incident (e.g., the apparent content

of the files that are being shared)?

2. What privacy considerations may impact the handling of this incident?

3. How would the handling of this incident differ if the computer performing peer-to-peer file

sharing also contains sensitive personally identifiable information?

Scenario 11: Unknown Wireless Access Point

On a Monday morning, the organization’s help desk receives calls from three users on the same floor of a

building who state that they are having problems with their wireless access. A network administrator who

is asked to assist in resolving the problem brings a laptop with wireless access to the users’ floor. As he

views his wireless networking configuration, he notices that there is a new access point listed as being

available. He checks with his teammates and determines that this access point was not deployed by his

team, so that it is most likely a rogue access point that was established without permission.

1. What should be the first major step in handling this incident (e.g., physically finding the rogue

access point, logically attaching to the access point)?

2. What is the fastest way to locate the access point? What is the most covert way to locate the

access point?

3. How would the handling of this incident differ if the access point had been deployed by an

external party (e.g., contractor) temporarily working at the organization’s office?

4. How would the handling of this incident differ if an intrusion detection analyst reported signs of

suspicious activity involving some of the workstations on the same floor of the building?

5. How would the handling of this incident differ if the access point had been removed while the

team was still attempting to physically locate it?

COMPUTER SECURITY INCIDENT HANDLING GUIDE

Appendix B—Incident-Related Data Elements

Organizations should identify a standard set of incident-related data elements to be collected for each

incident. This effort will not only facilitate more effective and consistent incident handling, but also assist

the organization in meeting applicable incident reporting requirements. The organization should designate

a set of basic elements (e.g., incident reporter’s name, phone number, and location) to be collected when

the incident is reported and an additional set of elements to be collected by the incident handlers during

their response. The two sets of elements would be the basis for the incident reporting database, previously

discussed in Section 3.2.5. The lists below provide suggestions of what information to collect for

incidents and are not intended to be comprehensive. Each organization should create its own list of

elements based on several factors, including its incident response team model and structure and its

definition of the term “incident.”

B.1 Basic Data Elements

 Contact Information for the Incident Reporter and Handler

– Name

– Role

– Organizational unit (e.g., agency, department, division, team) and affiliation

– Email address

– Phone number

– Location (e.g., mailing address, office room number)

 Incident Details

– Status change date/timestamps (including time zone): when the incident started, when the

incident was discovered/detected, when the incident was reported, when the incident was

resolved/ended, etc.

– Physical location of the incident (e.g., city, state)

– Current status of the incident (e.g., ongoing attack)

– Source/cause of the incident (if known), including hostnames and IP addresses

– Description of the incident (e.g., how it was detected, what occurred)

– Description of affected resources (e.g., networks, hosts, applications, data), including systems’

hostnames, IP addresses, and function

– If known, incident category, vectors of attack associated with the incident, and indicators related

to the incident (traffic patterns, registry keys, etc.)

– Prioritization factors (functional impact, information impact, recoverability, etc.)

– Mitigating factors (e.g., stolen laptop containing sensitive data was using full disk encryption)

– Response actions performed (e.g., shut off host, disconnected host from network)

– Other organizations contacted (e.g., software vendor)

 General Comments

COMPUTER SECURITY INCIDENT HANDLING GUIDE

B.2 Incident Handler Data Elements

 Current Status of the Incident Response

 Summary of the Incident

 Incident Handling Actions

– Log of actions taken by all handlers

– Contact information for all involved parties

– List of evidence gathered

 Incident Handler Comments

 Cause of the Incident (e.g., misconfigured application, unpatched host)

 Cost of the Incident

 Business Impact of the Incident

The business impact of the incident could either be a description of the incident’s effect (e.g., accounting department unable

to perform tasks for two days) or an impact category based on the cost (e.g., a “major” incident has a cost of over $100,000).

COMPUTER SECURITY INCIDENT HANDLING GUIDE

Appendix C—Glossary

Selected terms used in the publication are defined below.

Baselining: Monitoring resources to determine typical utilization patterns so that significant deviations

can be detected.

Computer Security Incident: See “incident.”

Computer Security Incident Response Team (CSIRT): A capability set up for the purpose of assisting

in responding to computer security-related incidents; also called a Computer Incident Response Team

(CIRT) or a CIRC (Computer Incident Response Center, Computer Incident Response Capability).

Event: Any observable occurrence in a network or system.

False Positive: An alert that incorrectly indicates that malicious activity is occurring.

Incident: A violation or imminent threat of violation of computer security policies, acceptable use

policies, or standard security practices.

Incident Handling: The mitigation of violations of security policies and recommended practices.

Incident Response: See “incident handling.”

Indicator: A sign that an incident may have occurred or may be currently occurring.

Intrusion Detection and Prevention System (IDPS): Software that automates the process of monitoring

the events occurring in a computer system or network and analyzing them for signs of possible incidents

and attempting to stop detected possible incidents.

Malware: A virus, worm, Trojan horse, or other code-based malicious entity that successfully infects a

host.

Precursor: A sign that an attacker may be preparing to cause an incident.

Profiling: Measuring the characteristics of expected activity so that changes to it can be more easily

identified.

Signature: A recognizable, distinguishing pattern associated with an attack, such as a binary string in a

virus or a particular set of keystrokes used to gain unauthorized access to a system.

Social Engineering: An attempt to trick someone into revealing information (e.g., a password) that can

be used to attack systems or networks.

Threat: The potential source of an adverse event.

Vulnerability: A weakness in a system, application, or network that is subject to exploitation or misuse.

COMPUTER SECURITY INCIDENT HANDLING GUIDE

Appendix D—Acronyms

Selected acronyms used in the publication are defined below.

CCIPS Computer Crime and Intellectual Property Section

CERIAS Center for Education and Research in Information Assurance and Security

CERT®/CC CERT® Coordination Center

CIO Chief Information Officer

CIRC Computer Incident Response Capability

CIRC Computer Incident Response Center

CIRT Computer Incident Response Team

CISO Chief Information Security Officer

CSIRC Computer Security Incident Response Capability

CSIRT Computer Security Incident Response Team

DDoS Distributed Denial of Service

DHS Department of Homeland Security

DNS Domain Name System

DoS Denial of Service

FAQ Frequently Asked Questions

FBI Federal Bureau of Investigation

FIPS Federal Information Processing Standards

FIRST Forum of Incident Response and Security Teams

FISMA Federal Information Security Management Act

GAO General Accountability Office

GFIRST Government Forum of Incident Response and Security Teams

GRS General Records Schedule

HTTP HyperText Transfer Protocol

IANA Internet Assigned Numbers Authority

IDPS Intrusion Detection and Prevention System

IETF Internet Engineering Task Force

IP Internet Protocol

IR Interagency Report

IRC Internet Relay Chat

ISAC Information Sharing and Analysis Center

ISP Internet Service Provider

IT Information Technology

ITL Information Technology Laboratory

MAC Media Access Control

MOU Memorandum of Understanding

MSSP Managed Security Services Provider

NAT Network Address Translation

NDA Non-Disclosure Agreement

NIST National Institute of Standards and Technology

NSRL National Software Reference Library

NTP Network Time Protocol

NVD National Vulnerability Database

OIG Office of Inspector General

OMB Office of Management and Budget

OS Operating System

PII Personally Identifiable Information

PIN Personal Identification Number

COMPUTER SECURITY INCIDENT HANDLING GUIDE

POC Point of Contact

REN-ISAC Research and Education Networking Information Sharing and Analysis Center

RFC Request for Comment

RID Real-Time Inter-Network Defense

SIEM Security Information and Event Management

SLA Service Level Agreement

SOP Standard Operating Procedure

SP Special Publication

TCP Transmission Control Protocol

TCP/IP Transmission Control Protocol/Internet Protocol

TERENA Trans-European Research and Education Networking Association

UDP User Datagram Protocol

URL Uniform Resource Locator

US-CERT United States Computer Emergency Readiness Team

VPN Virtual Private Network

COMPUTER SECURITY INCIDENT HANDLING GUIDE

Appendix E—Resources

The lists below provide examples of resources that may be helpful in establishing and maintaining an

incident response capability.

Incident Response Organizations

Organization

URL

Anti-Phishing Working Group (APWG)

http://www.antiphishing.org/

Computer Crime and Intellectual Property Section (CCIPS), U.S.

Department of Justice

http://www.cybercrime.gov/

CERT® Coordination Center, Carnegie Mellon University (CERT®/CC)

http://www.cert.org/

European Network and Information Security Agency (ENISA)

http://www.enisa.europa.eu/activities/cert

Forum of Incident Response and Security Teams (FIRST)

http://www.first.org/

Government Forum of Incident Response and Security Teams

(GFIRST)

http://www.us-cert.gov/federal/gfirst.html

High Technology Crime Investigation Association (HTCIA)

http://www.htcia.org/

InfraGard

http://www.infragard.net/

Internet Storm Center (ISC)

http://isc.sans.edu/

National Council of ISACs

http://www.isaccouncil.org/

United States Computer Emergency Response Team (US-CERT)

http://www.us-cert.gov/

NIST Publications

Resource Name

URL

NIST SP 800-53 Revision 3, Recommended Security

Controls for Federal Information Systems and

Organizations

http://csrc.nist.gov/publications/PubsSPs.html#800-53

NIST SP 800-83, Guide to Malware Incident Prevention

and Handling

http://csrc.nist.gov/publications/PubsSPs.html#800-83

NIST SP 800-84, Guide to Test, Training, and Exercise

Programs for IT Plans and Capabilities

http://csrc.nist.gov/publications/PubsSPs.html#800-84

NIST SP 800-86, Guide to Integrating Forensic

Techniques into Incident Response

http://csrc.nist.gov/publications/PubsSPs.html#800-86

NIST SP 800-92, Guide to Computer Security Log

Management

http://csrc.nist.gov/publications/PubsSPs.html#800-92

NIST SP 800-94, Guide to Intrusion Detection and

Prevention Systems (IDPS)

http://csrc.nist.gov/publications/PubsSPs.html#800-94

NIST SP 800-115, Technical Guide to Information

Security Testing and Assessment

http://csrc.nist.gov/publications/PubsSPs.html#800-115

NIST SP 800-128, Guide for Security-Focused

Configuration Management of Information Systems

http://csrc.nist.gov/publications/PubsSPs.html#800-128

COMPUTER SECURITY INCIDENT HANDLING GUIDE

Data Exchange Specifications Applicable to Incident Handling

Title

Description

Additional Information

Asset Identification

http://csrc.nist.gov/publications/ PubsNISTIRs.html#NIST-

IR-7693

ARF

Asset Results Format

http://csrc.nist.gov/publications/ PubsNISTIRs.html#NIST-

IR-7694

CAPEC

Common Attack Pattern Enumeration

and Classification

http://capec.mitre.org/

CCE

Common Configuration Enumeration

http://cce.mitre.org/

CEE

Common Event Expression

http://cee.mitre.org/

CPE

Common Platform Enumeration

http://cpe.mitre.org/

CVE

Common Vulnerabilities and Exposures

http://cve.mitre.org/

CVSS

Common Vulnerability Scoring System

http://www.first.org/cvss/cvss-guide

CWE

Common Weakness Enumeration

http://cwe.mitre.org/

CybOX

Cyber Observable eXpression

http://cybox.mitre.org/

MAEC

Malware Attribute Enumeration and

Characterization

http://maec.mitre.org/

OCIL

Open Checklist Interactive Language

http://csrc.nist.gov/publications/ PubsNISTIRs.html#NIST-

IR-7692

OVAL

Open Vulnerability Assessment

Language

http://oval.mitre.org/

RFC 4765

Intrusion Detection Message Exchange

Format (IDMEF)

http://www.ietf.org/rfc/rfc4765.txt

RFC 5070

Incident Object Description Exchange

Format (IODEF)

http://www.ietf.org/rfc/rfc5070.txt

RFC 5901

Extensions to the IODEF for Reporting

Phishing

http://www.ietf.org/rfc/rfc5901.txt

RFC 5941

Sharing Transaction Fraud Data

http://www.ietf.org/rfc/rfc5941.txt

RFC 6545

Real-time Inter-network Defense (RID)

http://www.ietf.org/rfc/rfc6545.txt

RFC 6546

Transport of Real-time Inter-network

Defense (RID) Messages over

HTTP/TLS

http://www.ietf.org/rfc/rfc6546.txt

SCAP

Security Content Automation Protocol

http://csrc.nist.gov/publications/PubsSPs.html #SP-800-

126-Rev.%202

XCCDF

Extensible Configuration Checklist

Description Format

http://csrc.nist.gov/publications/ PubsNISTIRs.html#NIST-

IR-7275-r4

COMPUTER SECURITY INCIDENT HANDLING GUIDE

Appendix F—Frequently Asked Questions

Users, system administrators, information security staff members, and others within organizations may

have questions about incident response. The following are frequently asked questions (FAQ).

Organizations are encouraged to customize this FAQ and make it available to their user community.

1. What is an incident?

In general, an incident is a violation of computer security policies, acceptable use policies, or

standard computer security practices. Examples of incidents are:

 An attacker commands a botnet to send high volumes of connection requests to one of an

organization’s web servers, causing it to crash.

 Users are tricked into opening a “quarterly report” sent via email that is actually malware;

running the tool has infected their computers and established connections with an external

host.

 A perpetrator obtains unauthorized access to sensitive data and threatens to release the details

to the press if the organization does not pay a designated sum of money.

 A user provides illegal copies of software to others through peer-to-peer file sharing services.

2. What is incident handling?

Incident handling is the process of detecting and analyzing incidents and limiting the incident’s

effect. For example, if an attacker breaks into a system through the Internet, the incident handling

process should detect the security breach. Incident handlers will then analyze the data and

determine how serious the attack is. The incident will be prioritized, and the incident handlers

will take action to ensure that the progress of the incident is halted and that the affected systems

return to normal operation as soon as possible.

3. What is incident response?

The terms “incident handling” and “incident response” are synonymous in this document.

4. What is an incident response team?

An incident response team (also known as a Computer Security Incident Response Team

[CSIRT]) is responsible for providing incident response services to part or all of an organization.

The team receives information on possible incidents, investigates them, and takes action to ensure

that the damage caused by the incidents is minimized.

5. What services does the incident response team provide?

The particular services that incident response teams offer vary widely among organizations.

Besides performing incident handling, most teams also assume responsibility for intrusion

detection system monitoring and management. A team may also distribute advisories regarding

new threats, and educate users and IT staff on their roles in incident prevention and handling.

6. To whom should incidents be reported?

Organizations should establish clear points of contact (POC) for reporting incidents internally.

Some organizations will structure their incident response capability so that all incidents are

reported directly to the incident response team, whereas others will use existing support

Definitions of “incident handling” and “incident response” vary widely. For example, CERT®/CC uses “incident handling”

to refer to the overall process of incident detection, reporting, analysis, and response, whereas “incident response” refers

specifically to incident containment, recovery, and notification of others. See http://www.cert.org/csirts/csirt_faq.html for

more information.

COMPUTER SECURITY INCIDENT HANDLING GUIDE

structures, such as the IT help desk, for an initial POC. The organization should recognize that

external parties, such as other incident response teams, would report some incidents. Federal

agencies are required under the law to report all incidents to the United States Computer

Emergency Readiness Team (US-CERT). All organizations are encouraged to report incidents to

their appropriate Computer Security Incident Response Teams (CSIRTs). If an organization does

not have its own CSIRT to contact, it can report incidents to other organizations, including

Information Sharing and Analysis Centers (ISACs).

7. How are incidents reported?

Most organizations have multiple methods for reporting an incident. Different reporting methods

may be preferable as a result of variations in the skills of the person reporting the activity, the

urgency of the incident, and the sensitivity of the incident. A phone number should be established

to report emergencies. An email address may be provided for informal incident reporting,

whereas a web-based form may be useful in formal incident reporting. Sensitive information can

be provided to the team by using a public key published by the team to encrypt the material.

8. What information should be provided when reporting an incident?

The more precise the information is, the better. For example, if a workstation appears to have

been infected by malware, the incident report should include as much of the following data as

practical:

 The user’s name, user ID, and contact information (e.g., phone number, email address)

 The workstation’s location, model number, serial number, hostname, and IP address

 The date and time that the incident occurred

 A step-by-step explanation of what happened, including what was done to the workstation

after the infection was discovered. This explanation should be detailed, including the exact

wording of messages, such as those displayed by the malware or by antivirus software alerts.

9. How quickly does the incident response team respond to an incident report?

The response time depends on several factors, such as the type of incident, the criticality of the

resources and data that are affected, the severity of the incident, existing Service Level

Agreements (SLA) for affected resources, the time and day of the week, and other incidents that

the team is handling. Generally, the highest priority is handling incidents that are likely to cause

the most damage to the organization or to other organizations.

10. When should a person involved with an incident contact law enforcement?

Communications with law enforcement agencies should be initiated by the incident response team

members, the chief information officer (CIO), or other designated official—users, system

administrators, system owners, and other involved parties should not initiate contact.

11. What should someone do who discovers that a system has been attacked?

The person should immediately stop using the system and contact the incident response team. The

person may need to assist in the initial handling of the incident—for instance, physically

monitoring the system until incident handlers arrive to protect evidence on the system.

12. What should someone do who is contacted by the media regarding an incident?

A person may answer the media’s questions in accordance with the organization’s policy

regarding incidents and outside parties. If the person is not qualified to represent the organization

in terms of discussing the incident, the person should make no comment regarding the incident,

COMPUTER SECURITY INCIDENT HANDLING GUIDE

other than to refer the caller to the organization’s public affairs office. This will allow the public

affairs office to provide accurate and consistent information to the media and the public.

COMPUTER SECURITY INCIDENT HANDLING GUIDE

Appendix G—Crisis Handling Steps

This is a list of the major steps that should be performed when a technical professional believes that a

serious incident has occurred and the organization does not have an incident response capability available.

This serves as a basic reference of what to do for someone who is faced with a crisis and does not have

time to read through this entire document.

1. Document everything. This effort includes every action that is performed, every piece of evidence,

and every conversation with users, system owners, and others regarding the incident.

2. Find a coworker who can provide assistance. Handling the incident will be much easier if two or

more people work together. For example, one person can perform actions while the other documents

them.

3. Analyze the evidence to confirm that an incident has occurred. Perform additional research as

necessary (e.g., Internet search engines, software documentation) to better understand the evidence.

Reach out to other technical professionals within the organization for additional help.

4. Notify the appropriate people within the organization. This should include the chief information

officer (CIO), the head of information security, and the local security manager. Use discretion when

discussing details of an incident with others; tell only the people who need to know and use

communication mechanisms that are reasonably secure. (If the attacker has compromised email

services, do not send emails about the incident.)

5. Notify US-CERT and/or other external organizations for assistance in dealing with the incident.

6. Stop the incident if it is still in progress. The most common way to do this is to disconnect affected

systems from the network. In some cases, firewall and router configurations may need to be modified

to stop network traffic that is part of an incident, such as a denial of service (DoS) attack.

7. Preserve evidence from the incident. Make backups (preferably disk image backups, not file system

backups) of affected systems. Make copies of log files that contain evidence related to the incident.

8. Wipe out all effects of the incident. This effort includes malware infections, inappropriate materials

(e.g., pirated software), Trojan horse files, and any other changes made to systems by incidents. If a

system has been fully compromised, rebuild it from scratch or restore it from a known good backup.

9. Identify and mitigate all vulnerabilities that were exploited. The incident may have occurred by

taking advantage of vulnerabilities in operating systems or applications. It is critical to identify such

vulnerabilities and eliminate or otherwise mitigate them so that the incident does not recur.

10. Confirm that operations have been restored to normal. Make sure that data, applications, and

other services affected by the incident have been returned to normal operations.

11. Create a final report. This report should detail the incident handling process. It also should provide

an executive summary of what happened and how a formal incident response capability would have

helped to handle the situation, mitigate the risk, and limit the damage more quickly.

COMPUTER SECURITY INCIDENT HANDLING GUIDE

Appendix H—Change Log

Revision 2 Draft 1—January 2012

Editorial:

 Tightened writing throughout publication

 Made minor formatting changes throughout publication

Technical Changes:

 Expanded material on information sharing (throughout Section 2)

 Updated incident reporting organization listings (Section 2.3.4.3)

 Updated list of common incident response team services (Section 2.5)

 Revised the incident response life cycle diagrams (throughout Section 3)

 Revamped the list of attack vectors (Section 3.2.1)

 Revamped the factors for incident handling prioritization (Section 3.2.6)

 Changed focus from identifying the attacker to identifying the attacking host (Section 3.3.3)

 Expanded the list of possible incident metrics (Section 3.4.2)

 Updated the incident handling scenarios to reflect current threats (old Appendix B, new Appendix A)

 Made minor updates to incident-related data field suggestions (old Appendix C, new Appendix B)

 Updated all of the tools and resources listings (old Appendix G, new Appendix E)

 Updated the Frequently Asked Questions and the Crisis Handling Steps to reflect changes made

elsewhere in the publication (old Appendices H and I, new Appendices F and G)

Deletions:

 Removed duplicate material on forensics, pointed readers to SP 800-86 for the same information

(Section 3.3.2)

 Deleted material specific to the old incident categories (Sections 4 through 8)

 Deleted the duplicate list of recommendations (old Appendix A)

 Deleted print resources list (old Appendix F)

 Deleted federal agency incident reporting categories (old Appendix J)

Revision 2 Final—August 2012

Editorial:

 Made minor revisions throughout publication

Technical Changes:

 Added information sharing as a team service (Section 2.5)

 Converted Table 3-1 into bulleted lists (Section 3.1.1)

 Added a mention of exercises (Section 3.1.1)

 Revised the attack vectors (formerly incident categories) (Section 3.2.1)

COMPUTER SECURITY INCIDENT HANDLING GUIDE

 Added SIEMs, network flows as common sources of precursors and indicators (Section 3.2.3)

 Expanded discussion of eradication and recovery (Section 3.3.4)

 Added a section on coordination and information sharing (Section 4)

 Added a table of data exchange specifications applicable to incident handling (Appendix E)

Computer Security Incident Handling Guide A.8 NIST 800 61r2 (2012)

A.8_NIST%20800-61r2%20Computer%20Security%20Incident%20Handling%20Guide%20(2012)

NIST.SP.800-61r2%20Incident%20Handling%20Guide

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