When discussing Incident Response, the concept of a lifecycle is frequently mentioned. Among the various approaches to Incident Response, one of the most commonly referenced and widely adopted frameworks is the lifecycle provided by the National Institute of Standards and Technology (NIST).

The NIST Incident Response Cycle, as outlined in SP 800-61, divides the process into four key stages:

Preparation: Establishing policies, tools, and resources to effectively handle incidents.
Detection and Analysis: Identifying and evaluating potential security incidents.
Containment, Eradication, and Recovery: Minimizing the impact, eliminating threats, and restoring normal operations.
Post-Incident Activity: Reviewing the response process to capture lessons learned and improve future incident handling.

IR-Nist source: [1]

It’s important to recognize that, in real-world scenarios, the stages of the incident response lifecycle often overlap and blend into one another. Smaller incidents may occur daily, requiring quick responses that don’t strictly follow a linear process. Therefore, it’s essential to understand that this lifecycle serves as a flexible framework to guide incident response, with movement back and forth between stages being a constant and natural part of the process.

1. Preparation

Cybersecurity is often underestimated, but even if everything seems fine now and no incidents have occurred, companies must take a proactive approach to prepare for potential cyberattacks. The Preparation stage is critical and encompasses a wide range of tasks tailored to an organization’s size and specific requirements.

This stage not only ensures a swift and effective response when an incident occurs—avoiding delays caused by confusion or lack of readiness—but also plays a key role in preventing incidents altogether. Essentially, the Preparation stage focuses on equipping the organization to both handle and prevent cyber threats.

Key areas to address during this stage include people, processes, and technology. Some practical examples are:

System hardening to reduce vulnerabilities.
Establishing contacts with essential third parties, such as legal firms.
Ensuring spare hardware is readily available.
Allocating funds for acquiring tools or resources during an incident.
Providing regular cybersecurity training to staff.
Developing detailed incident response playbooks.

In real-world scenarios, thorough preparation and upfront decision-making are essential to give a company the best chance of successfully responding to incidents.

2. Detection & Analysis

Detection

To handle an incident, the first step is knowing it exists. Effective detection and analysis require systems like EDR (Endpoint Detection and Response), IDR (Incident Detection and Response), SIEM (Security Information and Event Management), and NDR (Network Detection and Response). These tools are vital not just for detecting threats but for analyzing and contextualizing them. Often, multiple software solutions must work together and be actively monitored to achieve reliable and efficient detection.

The scale of detection efforts depends on the company’s size. Basic incidents are often flagged by tools like EDR, but sophisticated attacks can slip through if there isn't a clear baseline for what "normal" activity looks like. Defining and understanding normal behavior is critical for spotting anomalies.

A good example of why having a baseline and knowing your systems is crucial can be illustrated with this scenario:

Company A has a strict policy that prohibits root logins to access their servers. Instead, all administrative tasks are performed through individual user accounts with elevated privileges. One day, an alert is triggered indicating a root login attempt on one of their servers.

This detection is only possible because Company A has established a baseline for its systems, defining what constitutes normal behavior. Without this baseline, the root login attempt might not have been flagged as unusual. In contrast, another company that regularly uses root logins for administrative tasks wouldn’t treat such activity as an anomaly.

This example highlights that defining and knowing what "normal" looks like for your specific environment is essential for identifying deviations that could indicate a potential threat.

Additionally, strong policies, rules, and automation are key to managing the vast amounts of data collected by sensors. Without these measures, the sheer volume of information could overwhelm response efforts, making it challenging to prioritize and respond effectively.

Analysis

When Indicators of Compromise (IOCs) or precursors are identified, the process moves to the analysis phase. In this critical phase, the goal is to gather as much information as possible about the incident. This step is essential, as the findings from the analysis directly guide the response strategy, including determining the priorities, actions, and overall approach to addressing the incident.

During the analysis phase, it’s essential to verify the incident, as real-world scenarios often generate numerous false positives that must be assessed and ruled out quickly. Beyond verification, we need to understand key aspects such as the attack vector, the scope of the incident, and the potential for lateral movement. This information forms the foundation for planning an effective response and setting priorities.

Incident prioritization is a critical step in this process, and several frameworks can help. For instance, the Common Vulnerability Scoring System (CVSS) is widely used to evaluate the severity of vulnerabilities and guide prioritization based on their potential impact.

3. Containment & Eradication

Note: During containment and eradication, ensure that evidence is gathered and preserved. Save relevant logs and indicators, such as IP addresses, timestamps, and other clues, which can help identify the attacker.

Containment

During the Containment stage, the primary goal is to stop the ongoing attack. This not only prevents the attacker from causing further damage or compromising additional systems but also provides the incident response team with the time needed to plan and execute an appropriate response.

Containment strategies can vary depending on the nature of the attack. Examples of containment measures include:

Shutting down a compromised system.
Isolating a system from the network.
Disabling breached user accounts.
Blocking malicious IP addresses or users.

When implementing containment measures, it is essential to consider factors such as system availability, downtime, and potential operational impact to ensure a balanced and effective response.

Eradication & Recovery

In this stage, the focus is on restoring systems to a clean, uninfected state.

Important: It’s crucial to understand how the attack occurred. Simply recovering the system without addressing the root cause allows the attacker to exploit the same vulnerability again. Ensure the system is fully secured and no longer susceptible to the same attack.

Eradication and recovery measures may include:

Reimaging systems
Updating firewall rules
Updating security policies
Removing malware
Changing passwords of breached accounts
Blocking malicious IPs

4. Post-Incident Activity

After dealing with an incident, it’s important for teams to take the time to reflect, learn, and improve. The goal is to figure out what worked, what didn’t, and how things can be done better next time.

Questions to consider:

How fast did the team respond?
Who did what and when?
What information was missing or needed sooner?
What went well, and what needs fixing?

These are the kinds of things teams should discuss openly after an incident.

It’s also essential to create proper reports and ensure any necessary data is preserved—whether for compliance, audits, or legal purposes.

Conclusion

Incident response is not a one-size-fits-all process. While frameworks like the NIST Incident Response Lifecycle provide an excellent starting point, every organization must adapt and tailor its approach to its unique needs, infrastructure, and risk profile. The key to effective incident response lies in flexibility, continuous improvement, and leveraging lessons learned from each incident.

By reflecting on what worked and what didn’t, refining processes, and ensuring that teams are prepared with the right tools and knowledge, organizations can build a robust incident response strategy. Ultimately, the goal is to minimize damage, protect critical assets, and be better equipped for future challenges.

Resources

[1.] NIST Computer Security Incident Handling Guide SP800-61