This CISM practice question tests your understanding of incident management. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
During the eradication phase of an incident response, which action is MOST critical to ensure the threat is fully removed?
Delete the malware files from the system.
Why wrong: May miss hidden components.
Reset passwords for all user accounts.
Why wrong: Important but not eradication of the threat itself.
Update antivirus signatures.
Why wrong: Preventive, not eradication.
Reimage all affected systems from known-good backups.
Only way to guarantee removal of persistent threats.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Reimage all affected systems from known-good backups.
Option B is correct because reimaging from known-good backups ensures no remnants of malware remain. Option A is not eradication but prevention. Option C may miss hidden malware. Option D is a post-eradication step.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Delete the malware files from the system.
Why it's wrong here
May miss hidden components.
Reset passwords for all user accounts.
Why it's wrong here
Important but not eradication of the threat itself.
Update antivirus signatures.
Why it's wrong here
Preventive, not eradication.
Reimage all affected systems from known-good backups.
Why this is correct
Only way to guarantee removal of persistent threats.
Related concept
Static NAT maps one inside address to one outside address.
Common exam traps
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CISM NAT questions on configuration and troubleshooting.
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FAQ
Incident Management — This question tests Incident Management — Static NAT maps one inside address to one outside address..
The correct answer is: Reimage all affected systems from known-good backups. — Option B is correct because reimaging from known-good backups ensures no remnants of malware remain. Option A is not eradication but prevention. Option C may miss hidden malware. Option D is a post-eradication step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CISM NAT questions on configuration and troubleshooting.
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 24, 2026
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.
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