Question

Difficulty: MediumIncident Response Process and Playbooks

Following a high-severity alert indicating a web shell has been uploaded to a public-facing corporate web server, an incident response team is deployed to handle the breach. Place the following incident response actions in the correct sequential order from earliest to latest according to the standard NIST Incident Response Lifecycle.

  1. 1Analyze web server access logs and system memory to determine the scope of compromise and identify uploaded web shell paths.
  2. 2Isolate the compromised web server from the internal network segment to prevent lateral movement.
  3. 3Remove the web shell backdoors, terminate unauthorized processes, and patch the application vulnerability.
  4. 4Restore the web application from a clean backup image, verify system integrity, and return it to active production.
  5. 5Conduct a post-incident meeting to document findings, update WAF rules, and improve the incident response playbook.

Answer

The correct sequence follows the standard NIST Incident Response Lifecycle: 1. Analyze web server access logs and system memory, 2. Isolate the compromised web server from the internal network, 3. Remove the web shell backdoors and patch the vulnerability, 4. Restore the web application from a clean backup image and return it to production, 5. Conduct a post-incident meeting to document findings and update WAF rules.
The standard NIST incident response methodology strictly mandates moving through Detection & Analysis, Containment, Eradication, Recovery, and Post-Incident Activity. First analyzing system memory and logs allows responders to understand the threat. Network isolation contains the incident from spreading. Eradicating the web shell and patching the vulnerability removes the threat. Restoring from a verified clean backup completes recovery. Finally, conducting a post-mortem review fulfills post-incident obligations.

Step-by-Step Solution

1
Scope and analyze the threat (Detection & Analysis)
Identified the web shell location and scope of access.
You must first analyze and understand the extent of an active breach before taking disruptive containment steps.
2
Isolate the affected system (Containment)
Prevented lateral movement across the internal enterprise network.
Containment limits operational damage while preserving volatile data for further analysis.
3
Eliminate the threat and vulnerability (Eradication)
Removed malicious web shell files and remediated the root application flaw.
Eradication ensures the attacker cannot maintain persistence once the system is re-exposed.
4
Restore system operations (Recovery)
Web server restored from clean state and validated in production.
Recovery tests and restores operational services safely.
5
Conduct post-incident activities (Post-Incident / Lessons Learned)
Playbooks updated and Web Application Firewall rules hardened.
Lessons learned feed back into the preparation phase to prevent future occurrences.

Key Concept

NIST Incident Response Lifecycle (Detection & Analysis → Containment → Eradication → Recovery → Post-Incident Activity)
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