How to Perform Incident Response

Are you looking to learn how to do incident response in the context of computer security? Then you've come to the right place! In this short guide, we discuss the steps involved in classic incident response, and ways that you can manage your own computer systems to decrease the probability of serious damage (and prevent other incidents from happening in the future)!

Man coding - incident response in the context of security

Incident Response

In computer security, incident response is the process of containing, analyzing, and remediating a security incident. The primary goal is to understand the nature of an attack and to determine its cause, halt its progress, and take steps to prevent recurrence. Incident response may also be referred to as intrusion investigation, intrusion response, incident handling, intrusion analysis and network security incident response.

The scope of incident response is limited to a specific attack or series of related attacks that affect an organization. Incident response activities usually include:

  • logging and documenting detected events
  • analyzing these events identifying the affected systems
  • isolating and containing the affected systems
  • remediating/repairing the affected systems
  • recovering the affected systems to normal operational status
  • restoring the affected systems to predefined configuration and settings
  • analyzing the root cause in order to develop countermeasures against similar future incidents, and
  • evaluating the effectiveness of implemented measures in preventing similar incidents from occurring in future.

Most incident responses start and end with three steps: containment, analysis, and remediation.

1. Containment: isolate the affected systems to prevent the incident from spreading

In general, containment begins with containing the incident on the immediate system and preventing it from spreading and/or escalating to other subsystems on a computer or network. The sooner that you contain the incident, the easier the rest of your work will be, so this is crucial.

Containment is done primarily by disabling or killing the process that is associated with the incident or by removing the malicious code from the affected systems. It is also often necessary to isolate the affected systems to prevent the incident from spreading and/or escalating to other subsystems, which can be done by using a firewall to prevent traffic from leaving the affected system and restricting access permissions of the affected system from the remainder of the network.

Containment can also be accomplished by taking the system offline or by shutting it down, though this may require a lot of coordination with other systems depending on how the system is connected to the rest of the network. This approach also offlines the computer or subnetwork for the duration of the incident response, which may be an unacceptable option for certain systems.

2. Assessment: understand the scope and impact of the incident

Assessment begins by determining what has been compromised and what data may have been stolen during the incident. This is done by looking at logs, reviewing the configuration for the affected systems, and looking for evidence of the incident by checking hard drive for malicious code. It's important that any assessment be in-depth and vigorous, since, sometimes, even a small file left unchecked can lead to a complete re-takeover of a system.

There are many tools to assist with this process. For example, incident handlers could use a tool like Windows Sysinternals' procdump to gather process and thread-related information from a system, or they could use a tool like Microsoft's Sysinternals Suite to gather more detailed information from the system. Evidence can be gathered and analyzed from the system to attempt to identify the root cause and the scope of the incident.

Close up of keyboard while performing incident response

3. Remediation: stop the incident (and help prevent future incidents of similar nature)

Remediation is the process of repairing the damage caused by the incident. This is done by fixing the vulnerabilities that allowed the incident to occur in the first place, restoring data and systems that were compromised, and implementing controls to prevent future incidents from occurring.

Fixing vulnerabilities is done by applying patches to systems and uninstalling software that has shown to have bugs or vulnerabilities. Most software, over time, will have patches that are released to fix specific vulnerabilities. If the software is outdated, then it is often best to simply uninstall it and find software that is patched and up-to-date.

Remediating compromised data is done by restoring files and recovering from backups. If data cannot be restored from backups, some systems allow for the use of "data carving" to "carve out" the data that needs to be recovered and then restore it to the drive. Additionally, systems that have been compromised should be reimaged with a known good (healthy) system image. This helps prevent the malware from reinstalling itself and maximizes your chances of keeping the system from being reinfected.

Lastly, implementing controls to prevent future incidents is done by examining the root cause and taking steps to protect the system. If the incident was caused by a vulnerability that has since been patched, then applying the appropriate security patch to the system is necessary to prevent the incident from occurring again. If the incident was caused by a piece of malware, then it is necessary to remediate the malware from the system through the use of antivirus software, firewalls, and other security measures.

Ultimately, by taking steps now to prepare for a security incident (such as establishing an incident response team, establishing procedures for incident response, and establishing procedures for handling data breaches), organizations can reduce the risks of an incident occurring in the first place. However, in the event that an incident does occur, it is important to have a plan for handling the incident to minimize the risk to your organization.


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