What is Incident Response?
Incident response (IR) is a structured methodology for handling security incidents, breaches, and cyber threats. A well-defined incident response plan allows you to effectively identify, minimize the damage, and reduce the cost of a cyber attack, while finding and fixing the cause to prevent future attacks.
During a cybersecurity incident, security teams will face many unknowns and a frenzy of activity. In such a hectic environment, they may fail to follow proper incident response procedures to effectively limit the damage. This is important because a security incident can be a high-pressure situation, and your IR team must immediately focus on the critical tasks at hand. Clear thinking and swiftly taking pre-planned incident response steps during a security incident can prevent many unnecessary business impacts and reputational damage.
You can help your team perform a complete, rapid and effective response to a cyber security incident by having a comprehensive incident response (IR) plan in place. In addition, completing an incident response plan checklist and developing and deploying an IR policy will help before you have fully developed your IR plan.
Incident response steps to take after a cybersecurity event occurs
The first priority is to prepare in advance by putting a concrete IR plan in place. Your organization should establish and battle-test a plan before a significant attack or data breach occurs. It should address the following response phases as defined by NIST Computer Security Incident Handling Guide (SP 800-61).
- Preparation – Planning in advance how to handle and prevent security incidents
- Detection and Analysis – Encompasses everything from monitoring potential attack vectors, to looking for signs of an incident, to prioritization
- Containment, Eradication, and Recovery – Developing a containment strategy, identifying and mitigating the hosts and systems under attack, and having a plan for recovery
- Post-Incident Activity – Reviewing lessons learned and having a plan for evidence retention
Figure 1 – The NIST recommended phases for responding to a cybersecurity incident
Building on the outlined NIST phases, here are specific incident response steps to take once a critical security event has been detected:
1. Assemble your team – It’s critical to have the right people with the right skills, along with associated tribal knowledge. Appoint a team leader who will have overall responsibility for responding to the incident. This person should have a direct line of communication with management so that important decisions—such as taking key systems offline if necessary—can be made quickly.
In smaller organizations, or where a threat isn’t severe, your SOC team or managed security consultants may be sufficient to handle an incident. But for the more serious incidents, you should include other relevant areas of the company such as corporate communications and human resources.
If you have built a Security Incident Response Team (CSIRT), now is the time to activate your team, bringing in the entire range of pre-designated technical and non-technical specialists.
If a breach could result in litigation, or requires public notification and remediation, you should notify your legal department immediately.
2. Detect and ascertain the source. The IR team you’ve assembled should first work to identify the cause of the breach, and then ensure that it’s contained.
Security teams will become aware that an incident is occurring or has occurred from a very wide variety of indicators, including:
- Users, system administrators, network administrators, security staff, and others from within your organization reporting signs of a security incident
- SIEMs or other security products generating alerts based on analysis of log data
- File integrity checking software, using hashing algorithms to detect when important files have been altered
- Anti-malware programs
- Logs (including audit-related data), which should be systematically reviewed to look at anomalous and suspicious activity with:
- External storage
- Real-time memory
- Network devices
- Operating systems
- Cloud services
3. Contain and recover – A security incident is analogous to a forest fire. Once you’ve detected an incident and its source, you need to contain the damage. This may involve disabling network access for computers known to be infected by viruses or other malware (so they can be quarantined) and installing security patches to resolve malware issues or network vulnerabilities. You may also need to reset passwords for users with accounts that were breached, or block accounts of insiders that may have caused the incident. Additionally, your team should back up all affected systems to preserve their current state for later forensics.
Next, move to any needed service restoration, which includes two critical steps:
- Perform system/network validation and testing to certify all systems as operational.
- Recertify any component that was compromised as both operational and secure.
Ensure your long-term containment strategy includes not only returning all systems to production to allow for standard business operation, but also locking down or purging user accounts and backdoors that enabled the intrusion.
4. Assess the damage and severity – Until the smoke clears it can be difficult to grasp the severity of an incident and the extent of damage it has caused. For example, did it result from an external attack on servers that could shut down critical business components such as an e-commerce or reservation systems? Or, for example, did a web application layer intrusion perform a SQL Injection attack to execute malicious SQL statements on a web application’s database or potentially use a web server as a pathway to steal data from or control critical backend systems? If critical systems are involved, escalate the incident and activate your CSIRT or response team immediately.
In general, look at the cause of the incident. In cases where there was a successful external attacker or malicious insider, consider the event as more severe and respond accordingly. At the right time, review the pros and cons of launching a full-fledged cyber attribution investigation.
5. Begin the notification process – A data breach is a security incident in which sensitive, protected or confidential data is copied, transmitted, viewed, stolen or used by an individual unauthorized person. Privacy laws such as GDPR and California’s SB1386 require public notification in the event of such a data breach. Notify affected parties so they can protect themselves from identity theft or other fallout from the disclosure of confidential personal or financial data. See Exabeam’s blog on how to create a breach notification letter in advance of a security incident.
6. Start now to prevent the same type of incident in the future – Once a security incident has been stabilized, examine lessons learned to prevent recurrences of similar incidents. This might include patching server vulnerabilities, training employees on how to avoid phishing scams, or rolling out technologies to better monitor insider threats. Fixing security flaws or vulnerabilities found during your post-incident activities is a given.
Also, review lessons learned from the incident and implement appropriate changes to your security policies with training for staff and employees. For example, if the attack resulted from an unwitting employee opening an Excel file as an email attachment, implement a company-wide policy and training on how to recognize and respond to a phishing email.
Lastly, update your security incident response plan to reflect all of these preventative measures.
Every organization will have different incident response steps based on their unique IT environment and business needs. Study industry guides such as those published by NIST to ensure your IR planning includes all the necessary incident response steps to protect your organization when a cybersecurity incident occurs.