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CISM Practice Question: During an incident investigation, the forensic…
During an incident investigation, the forensic analyst discovers that a malware sample communicates with an external IP address. The organization's incident response plan requires a decision on whether to block the IP at the firewall. What should the incident response team do FIRST?
⚠ Common exam trap
It's easy for candidates to choose 'Block the IP immediately' (Option B) because they equate speed with effective containment, but CISM stresses that containment actions must be risk-informed and validated to avoid collateral damage and legal liability.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Check threat intelligence feeds to confirm maliciousness.
The incident response team must first validate the maliciousness of the IP address using threat intelligence feeds before taking any irreversible action. Blocking an IP without confirmation could disrupt legitimate business operations or tip off an attacker, and the CISM framework emphasizes evidence-based decision-making during incident response.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Monitor the connection further without taking action.
Why it's wrong here
Passive monitoring leaves the command-and-control channel open, permitting data exfiltration or further payload delivery while the team watches. It is tempting during threat intelligence gathering, where observing adversary behaviour to identify additional infrastructure is the goal, but the plan here requires a containment decision.
- ✗
Block the IP address immediately to prevent data exfiltration.
Why it's wrong here
Blocking first destroys the attacker's command-and-control channel and any evidence of exfiltration scope, contradicting forensic preservation. Immediate blocking suits containment once the investigation has captured indicators and assessed impact. The stem's requirement is a decision, so analysis must precede action.
- ✗
Notify law enforcement about the IP address.
Why it's wrong here
Law enforcement notification is an external escalation step that does not inform the immediate containment decision the plan demands; blocking or monitoring must be decided first. It is tempting because reporting criminal activity is a legal and regulatory obligation, but that occurs after containment, not before it.
- ✓
Check threat intelligence feeds to confirm maliciousness.
Why this is correct
Confirming the IP is genuinely malicious through threat intelligence prevents blocking legitimate business partners or shared infrastructure, which could disrupt operations. Verification establishes attribution and confidence before firewall changes, aligning with the plan's requirement for a defensible blocking decision.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CISM practice question is part of Courseiva's free ISACA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CISM exam.