special Publication 800-12: An Introduction to Computer Security: The NIST Handbook

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CHAPTER 12:
Computer Security Incident Handling

Computer systems are subject to a wide range of mishaps -- from corrupted data files, to viruses, to natural disasters. Some of these mishaps can be fixed through standard operating procedures. For example, frequently occurring events (e.g., a mistakenly deleted file) can usually be readily repaired (e.g., by restoration from the backup file). More severe mishaps, such as outages caused by natural disasters, are normally addressed in an organization's contingency plan. Other damaging events result from deliberate malicious technical activity (e.g., the creation of viruses or system hacking).

Malicious code include viruses as well as Trojan horses and worms. A virus is a code segment that replicates by attaching copies of itself to existing executables. A Trojan horse is a program that performs a desired task, but also includes unexpected functions. A worm is a self-replicating program.

A computer security incident can result from a computer virus, other malicious code, or a system intruder, either an insider or an outsider. It is used in this chapter to broadly refer to those incidents resulting from deliberate malicious technical activity.⁹⁰ It can more generally refer to those incidents that, without technically expert response, could result in severe damage.⁹¹ This definition of a computer security incident is somewhat flexible and may vary by organization and computing environment.

Although the threats that hackers and malicious code pose to systems and networks are well known, the occurrence of such harmful events remains unpredictable. Security incidents on larger networks (e.g., the Internet), such as break-ins and service disruptions, have harmed various organizations' computing capabilities. When initially confronted with such incidents, most organizations respond in an ad hoc manner. However recurrence of similar incidents often makes it cost-beneficial to develop a standing capability for quick discovery of and response to such events. This is especially true, since incidents can often "spread" when left unchecked thus increasing damage and seriously harming an organization.

Incident handling is closely related to contingency planning as well as support and operations. An incident handling capability may be viewed as a component of contingency planning, because it provides the ability to react quickly and efficiently to disruptions in normal processing. Broadly speaking, contingency planning addresses events with the potential to interrupt system operations. Incident handling can be considered that portion of contingency planning that responds to malicious technical threats.

This chapter describes how organizations can address computer security incidents (in the context of their larger computer security program) by developing a computer security incident handling capability.⁹²

Many organizations handle incidents as part of their user support capability (discussed in Chapter 14) or as a part of general system support.

12.1 Benefits of an Incident Handling Capability

The primary benefits of an incident handling capability are containing and repairing damage from incidents, and preventing future damage. In addition, there are less obvious side benefits related to establishing an incident handling capability.

12.1.1 Containing and Repairing Damage from Incidents

Some organizations suffer repeated outbreaks of viruses because the viruses are never completely eradicated. For example suppose two LANs, Personnel and Budget, are connected, and a virus has spread within each. The administrators of each LAN detect the virus and decide to eliminate it on their LAN. The Personnel LAN administrator first eradicates the virus, but since the Budget LAN is not yet virus-free, the Personnel LAN is reinfected. Somewhat later, the Budget LAN administrator eradicates the virus. However, the virus reinfects the Budget LAN from the Personnel LAN. Both administrators may think all is well, but both are reinfected. An incident handling capability allows organizations to address recovery and containment of such incidents in a skilled, coordinated manner.

When left unchecked, malicious software can significantly harm an organization's computing, depending on the technology and its connectivity. An incident handling capability provides a way for users to report incidents⁹³ and the appropriate response and assistance to be provided to aid in recovery. Technical capabilities (e.g., trained personnel and virus identification software) are prepositioned, ready to be used as necessary. Moreover, the organization will have already made important contacts with other supportive sources (e.g., legal, technical, and managerial) to aid in containment and recovery efforts.

Without an incident handling capability, certain responses -- although well intentioned -- can actually make matters worse. In some cases, individuals have unknowingly infected anti-virus software with viruses and then spread them to other systems. When viruses spread to local area networks (LANs), most or all of the connected computers can be infected within hours. Moreover, uncoordinated efforts to rid LANs of viruses can prevent their eradication.

Many organizations use large LANs internally and also connect to public networks, such as the Internet. By doing so, organizations increase their exposure to threats from intruder activity, especially if the organization has a high profile (e.g., perhaps it is involved in a controversial program). An incident handling capability can provide enormous benefits by responding quickly to suspicious activity and coordinating incident handling with responsible offices and individuals, as necessary. Intruder activity, whether hackers or malicious code, can often affect many systems located at many different network sites; thus, handling the incidents can be logistically complex and can require information from outside the organization. By planning ahead, such contacts can be preestablished and the speed of response improved, thereby containing and minimizing damage. Other organizations may have already dealt with similar situations and may have very useful guidance to offer in speeding recovery and minimizing damage.

12.1.2 Preventing Future Damage

An incident handling capability also assists an organization in preventing (or at least minimizing) damage from future incidents. Incidents can be studied internally to gain a better understanding of the organization's threats and vulnerabilities so more effective safeguards can be implemented. Additionally, through outside contacts (established by the incident handling capability) early warnings of threats and vulnerabilities can be provided. Mechanisms will already be in place to warn users of these risks.

The incident handling capability allows an organization to learn from the incidents that it has experienced. Data about past incidents (and the corrective measures taken) can be collected. The data can be analyzed for patterns -- for example, which viruses are most prevalent, which corrective actions are most successful, and which systems and information are being targeted by hackers. Vulnerabilities can also be identified in this process -- for example, whether damage is occurring to systems when a new software package or patch is used. Knowledge about the types of threats that are occurring and the presence of vulnerabilities can aid in identifying security solutions. This information will also prove useful in creating a more effective training and awareness program -- and thus help reduce the potential for losses. The incident handling capability assists the training and awareness program by providing information to users as to (1) measures that can help avoid incidents (e.g., virus scanning) and (2) what should be done in case an incident does occur.

The sharing of incident data among organizations can help at both the national and the international levels to prevent and respond to breaches of security in a timely, coordinated manner.

Of course, the organization's attempts to prevent future losses does not occur in a vacuum. With a sound incident handling capability, contacts will have been established with counterparts outside the organization. This allows for early warning of threats and vulnerabilities that the organization may have not yet experienced. Early preventative measures (generally more cost-effective than repairing damage) can then be taken to reduce future losses. Data is also shared outside the organization to allow others to learn from the organization's experiences.

12.1.3 Side Benefits

Finally, establishing an incident handling capability helps an organization in perhaps unanticipated ways. Three are discussed here.

Uses of Threat and Vulnerability Data. Incident handling can greatly enhance the risk assessment process. An incident handling capability will allow organizations to collect threat data that may be useful in their risk assessment and safeguard selection processes (e.g., in designing new systems). Incidents can be logged and analyzed to determine whether there is a recurring problem (or if other patterns are present, as are sometimes seen in hacker attacks), which would not be noticed if each incident were only viewed in isolation. Statistics on the numbers and types of incidents in the organization can be used in the risk assessment process as an indication of vulnerabilities and threats.⁹⁴

Enhancing Internal Communications and Organization Preparedness. Organizations often find that an incident handling capability enhances internal communications and the readiness of the organization to respond to any type of incident, not just computer security incidents. Internal communications will be improved; management will be better organized to receive communications; and contacts within public affairs, legal staff, law enforcement, and other groups will have been preestablished. The structure set up for reporting incidents can also be used for other purposes.

Enhancing the Training and Awareness Program. The organization's training process can also benefit from incident handling experiences. Based on incidents reported, training personnel will have a better understanding of users' knowledge of security issues. Trainers can use actual incidents to vividly illustrate the importance of computer security. Training that is based on current threats and controls recommended by incident handling staff provides users with information more specifically directed to their current needs -- thereby reducing the risks to the organization from incidents.

12.2 Characteristics of a Successful Incident Handling Capability

A successful incident handling capability has several core characteristics:

• an understanding of the constituency it will serve;


• an educated constituency;


• a means for centralized communications;


• expertise in the requisite technologies; and


• links to other groups to assist in incident handling (as needed)

12.2.1 Defining the Constituency to Be Served

The focus of a computer security incident handling capability may be external as well as internal. An incident that affects an organization may also affect its trading partners, contractors, or clients. In addition, an organization's computer security incident handling capability may be able to help other organizations and, therefore, help protect the community as a whole.

The constituency includes computer users and program managers. Like any other customer-vendor relationship, the constituency will tend to take advantage of the capability if the services rendered are valuable.

The constituency is not always the entire organization. For example, an organization may use several types of computers and networks but may decide that its incident handling capability is cost-justified only for its personal computer users. In doing so, the organization may have determined that computer viruses pose a much larger risk than other malicious technical threats on other platforms. Or, a large organization composed of several sites may decide that current computer security efforts at some sites do not require an incident handling capability, whereas other sites do (perhaps because of the criticality of processing).

12.2.2 Educated Constituency

Managers need to know details about incidents, including who discovered them and how, so that they can prevent similar incidents in the future. However users will not be forthcoming if they fear reprisal or that they will become scapegoats. Organizations may need to offer incentives to employees for reporting incidents and offer guarantees against reprisal or other adverse actions. It may also be useful to consider anonymous reporting.

Users need to know about, accept, and trust the incident handling capability or it will not be used. Through training and awareness programs, users can become knowledgeable about the existence of the capability and how to recognize and report incidents. Users trust in the value of the service will build with reliable performance.

12.2.3 Centralized Reporting and Communications

Successful incident handling requires that users be able to report incidents to the incident handling team in a convenient, straightforward fashion; this is referred to as centralized reporting. A successful incident handling capability depends on timely reporting. If it is difficult or time consuming to report incidents, the incident handling capability may not be fully used. Usually, some form of a hotline, backed up by pagers, works well.

Centralized communications is very useful for accessing or distributing information relevant to the incident handling effort. For example, if users are linked together via a network, the incident handling capability can then use the network to send out timely announcements and other information. Users can take advantage of the network to retrieve security information stored on servers and communicate with the incident response team via e-mail.

12.2.4 Technical Platform and Communications Expertise

The technical staff members who comprise the incident handling capability need specific knowledge, skills, and abilities. Desirable qualifications for technical staff members may include the ability to:

• work expertly with some or all of the constituency's core technology;


• work in a group environment;


• communicate effectively with different types of users, who will range from system administrators to unskilled users to management to law-enforcement officials;


• be on-call 24 hours as needed; and


• travel on short notice (of course, this depends upon the physical location of the constituency to be served).

12.2.5 Liaison With Other Organizations

Due to increasing computer connectivity, intruder activity on networks can affect many organizations, sometimes including those in foreign countries. Therefore, an organization's incident handling team may need to work with other teams or security groups to effectively handle incidents that range beyond its constituency. Additionally, the team may need to pool its knowledge with other teams at various times. Thus, it is vital to the success of an incident handling capability that it establish ties and contacts with other related counterparts and supporting organizations.

The Forum of Incident Response and Security Teams The 1988 Internet worm incident highlighted the need for better methods for responding to and sharing information about incidents. It was also clear that any single team or "hot line" would simply be overwhelmed. Out of this was born the concept of a coalition of response teams -- each with its own constituency, but working together to share information, provide alerts, and support each other in the response to incidents. The Forum of Incident Response and Security Teams (FIRST) includes teams from government, industry, computer manufacturers, and academia. NIST serves as the secretariat of FIRST.

Especially important to incident handling are contacts with investigative agencies, such as federal (e.g., the FBI), state, and local law enforcement. Laws that affect computer crime vary among localities and states, and some actions may be state (but not federal) crimes. It is important for teams to be familiar with current laws and to have established contacts within law enforcement and investigative agencies.

Incidents can also garner much media attention and can reflect quite negatively on an organization's image. An incident handling capability may need to work closely with the organization's public affairs office, which is trained in dealing with the news media. In presenting information to the press, it is important that (1) attackers are not given information that would place the organization at greater risk and (2) potential legal evidence is properly protected.

12.3 Technical Support for Incident Handling

Incident handling will be greatly enhanced by technical mechanisms that enable the dissemination of information quickly and conveniently.

12.3.1 Communications for Centralized Reporting of Incidents

The technical ability to report incidents is of primary importance, since without knowledge of an incident, response is precluded. Fortunately, such technical mechanisms are already in place in many organizations.

For rapid response to constituency problems, a simple telephone "hotline" is practical and convenient. Some agencies may already have a number used for emergencies or for obtaining help with other problems; it may be practical (and cost-effective) to also use this number for incident handling. It may be necessary to provide 24-hour coverage for the hotline. This can be done by staffing the answering center, by providing an answering service for non-office hours, or by using a combination of an answering machine and personal pagers.

One way to establish a centralized reporting and incident response capability, while minimizing expenditures, is to use an existing Help Desk. Many agencies already have central Help Desks for fielding calls about commonly used applications, troubleshooting system problems, and providing help in detecting and eradicating computer viruses. By expanding the capabilities of the Help Desk and publicizing its telephone number (or e-mail address), an agency may be able to significantly improve its ability to handle many different types of incidents at minimal cost.

If additional mechanisms for contacting the incident handling team can be provided, it may increase access and thus benefit incident handling efforts. A centralized e-mail address that forwards mail to staff members would permit the constituency to conveniently exchange information with the team. Providing a fax number to users may also be helpful.

12.3.2 Rapid Communications Facilities

Some form of rapid communications is essential for quickly communicating with the constituency as well as with management officials and outside organizations. The team may need to send out security advisories or collect information quickly, thus some convenient form of communications, such as electronic mail, is generally highly desirable. With electronic mail, the team can easily direct information to various subgroups within the constituency, such as system managers or network managers, and broadcast general alerts to the entire constituency as needed. When connectivity already exists, e-mail has low overhead and is easy to use. (However, it is possible for the e-mail system itself to be attacked, as was the case with the 1988 Internet worm.)

Although there are substitutes for e-mail, they tend to increase response time. An electronic bulletin board system (BBS) can work well for distributing information, especially if it provides a convenient user interface that encourages its use. A BBS connected to a network is more convenient to access than one requiring a terminal and modem; however, the latter may be the only alternative for organizations without sufficient network connectivity. In addition, telephones, physical bulletin boards, and flyers can be used.

12.3.3 Secure Communications Facilities

Incidents can range from the trivial to those involving national security. Often when exchanging information about incidents, using encrypted communications may be advisable. This will help prevent the unintended distribution of incident-related information. Encryption technology is available for voice, fax, and e-mail communications.

12.4 Interdependencies

An incident handling capability generally depends upon other safeguards presented in this handbook. The most obvious is the strong link to other components of the contingency plan. The following paragraphs detail the most important of these interdependencies.

Contingency Planning. As discussed in the introduction to this chapter, an incident handling capability can be viewed as the component of contingency planning that deals with responding to technical threats, such as viruses or hackers. Close coordination is necessary with other contingency planning efforts, particularly when planning for contingency processing in the event of a serious unavailability of system resources.

Support and Operations. Incident handling is also closely linked to support and operations, especially user support and backups. For example, for purposes of efficiency and cost savings, the incident handling capability is often co-operated with a user "help desk." Also, backups of system resources may need to be used when recovering from an incident.

Training and Awareness. The training and awareness program can benefit from lessons learned during incident handling. Incident handling staff will be able to help assess the level of user awareness about current threats and vulnerabilities. Staff members may be able to help train system administrators, system operators, and other users and systems personnel. Knowledge of security precautions (resulting from such training) helps reduce future incidents. It is also important that users are trained what to report and how to report it.

Risk Management. The risk analysis process will benefit from statistics and logs showing the numbers and types of incidents that have occurred and the types of controls that are effective in preventing incidents. This information can be used to help select appropriate security controls and practices.

12.5 Cost Considerations

There are a number of start-up costs and funding issues to consider when planning an incident handling capability. Because the success of an incident handling capability relies so heavily on users' perceptions of its worth and whether they use it, it is very important that the capability be able to meet users' requirements. Two important funding issues are:

Personnel. An incident handling capability plan might call for at least one manager and one or more technical staff members (or their equivalent) to accomplish program objectives. Depending on the scope of the effort, however, full-time staff members may not be required. In some situations, some staff may be needed part-time or on an on-call basis. Staff may be performing incident handling duties as an adjunct responsibility to their normal assignments.

Education and Training. Incident handling staff will need to keep current with computer system and security developments. Budget allowances need to be made, therefore, for attending conferences, security seminars, and other continuing-education events. If an organization is located in more than one geographic areas, funds will probably be needed for travel to other sites for handling incidents.

References

Brand, Russell L. Coping With the Threat of Computer Security Incidents: A Primer from Prevention Through Recovery. July 1989.

Fedeli, Alan. "Organizing a Corporate Anti-Virus Effort." Proceedings of the Third Annual Computer VIRUS Clinic, Nationwide Computer Corp. March 1990.

Holbrook, P., and J. Reynolds, eds. Site Security Handbook. RFC 1244 prepared for the Internet Engineering Task Force, 1991.

National Institute of Standards and Technology. "Establishing a Computer Security Incident Response Capability." Computer Systems Laboratory Bulletin. Gaithersburg, MD. February 1992.

Padgett, K. Establishing and Operating an Incident Response Team. Los Alamos, NM: Los Alamos National Laboratory, 1992.

Pethia, Rich, and Kenneth van Wyk. Computer Emergency Response - An International Problem. 1990.

Quarterman, John. The Matrix - Computer Networks and Conferencing Systems Worldwide. Digital Press, 1990.

Scherlis, William, S. Squires, and R. Pethia. Computer Emergency Response. 1989.

Schultz, E., D. Brown, and T. Longstaff. Responding to Computer Security Incidents: Guidelines for Incident Handling. University of California Technical Report UCRL-104689, 1990.

Proceedings of the Third Invitational Workshop on Computer Security Incident Response. August 1991.

Wack, John. Establishing an Incident Response Capability. Special Publication 800-3. Gaithersburg, MD: National Institute of Standards and Technology. November 1991.

Footnotes:

90. Organizations may wish to expand this to include, for example, incidents of theft.
91. Indeed, damage may result, despite the best efforts to the contrary.
92. See NIST Special Publication 800-3, Establishing an Incident Response Capability, November 1991.
93. A good incident handling capability is closely linked to an organization's training and awareness program. It will have educated users about such incidents and what to do when they occur. This can increase the likelihood that incidents will be reported early, thus helping to minimize damage.
94. It is important, however, not to assume that since only n reports were made, that n is the total number of incidents; it is not likely that all incidents will be reported.