The Six Phases of Incident Response

Threat actors are becoming more sophisticated, and organizations must be prepared to detect, contain, and remediate incidents swiftly. The incident response (IR) process ensures that security teams can minimize damage, recover systems, and strengthen defenses against future threats. 

A well-structured incident response process as set out by both SANS and NIST follows six key phases:

1. Preparation

Before an incident occurs, organizations must establish clear policies, deploy security tools, and train teams to respond effectively. Preparation includes:

• Developing an Incident Response Plan (IRP) that outlines roles, responsibilities, and procedures.
• Conducting regular risk assessments to identify potential threats.
• Implementing logging and monitoring solutions to detect anomalies early.
• Training employees on security awareness to reduce human error-related incidents.

2. Identification

Detection is the first step in an active response. Security teams must determine if an anomaly is a real incident. This is done by:

• Monitoring alerts from SIEMs, EDRs, cloud security tools, and network logs.
• Investigating unusual system behavior, unauthorized access, or data exfiltration attempts.
• Using forensic analysis and threat intelligence to confirm whether an attack has occurred.

Key challenge: False positives can overwhelm teams, so prioritizing alerts based on severity and impact is crucial.

3. Containment

Once an incident is identified, the focus shifts to limiting its impact. Containment can be either short-term (immediate response) or long-term (strategic mitigation).

• Short-term containment:
  • Isolating infected systems to prevent lateral movement.
  • Blocking malicious domains, IPs, or compromised accounts.
• Long-term containment:
  • Deploying security patches or configurations.
  • Strengthening access controls to prevent reinfection.

4. Eradication

After containment, the root cause must be removed to prevent further damage. This includes:

• Removing malware, backdoors, or persistence mechanisms from affected systems.
• Conducting deep forensic analysis to ensure no remnants of the attack remain.
• Implementing additional security measures, such as improved endpoint protection or stronger authentication.

Best practice: Organizations should leverage cloud forensics and automation to speed up the eradication process, ensuring attackers don’t regain access.

5. Recovery

The goal is to restore normal operations while ensuring security measures are in place. This phase includes:

• Restoring systems from clean backups.
• Monitoring for signs of reinfection.
• Conducting post-recovery testing to ensure vulnerabilities have been addressed.

Cloud-specific consideration: If the attack involved cloud infrastructure, ensure security groups, IAM roles, and storage permissions are reviewed and tightened.

6. Lessons Learned

The final phase involves documenting the incident, analyzing response effectiveness, and making improvements. Key steps include:

• Writing an incident report detailing attack vectors, response actions, and remediation efforts.
• Conducting post-incident reviews (PIRs) to identify gaps in defenses.
• Updating security policies, tools, or response plans based on new insights.

Proactive step: Sharing intelligence with the broader security community (e.g., MITRE ATT&CK, ISACs) can help others defend against similar threats.

Want to learn how Cado Security can help you accelerate forensic investigations? Contact our team to request a demo today.