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CISM Practice Question: After a ransomware attack, a company discovers…
After a ransomware attack, a company discovers that backups are also encrypted. The incident response team has isolated the affected systems. What should be the next step?
⚠ Common exam trap
The trap here is that candidates often jump to recovery actions (like reimaging or restoring backups) without first ensuring containment and legal notification, confusing the order of the Incident Response phases.
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
✓
Isolate additional systems and notify law enforcement.
After isolating affected systems, the next priority is to contain the incident by identifying and isolating any additional compromised systems to prevent further spread, and to notify law enforcement as required by legal and regulatory obligations. This aligns with the Incident Response (IR) process, specifically the Containment, Eradication, and Recovery phases, where containment must precede any recovery attempts to avoid re-infection.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Attempt restoration from encrypted backups.
Why it's wrong here
Encrypted backups cannot be read without the attacker's keys, so restoration simply fails and wastes the recovery window. It is tempting because restoring from backup is normally the first recovery action after containment, and would be correct had the backup copies remained outside the encryption scope.
- ✗
Pay the ransom to obtain decryption keys.
Why it's wrong here
Paying does not restore operations and funds criminal activity, while offering no guarantee of working keys; containment and eradication from clean media remain the priority. It is tempting when no usable backups exist and leadership wants the fastest route to decryption, but it addresses data recovery rather than incident response.
- ✓
Isolate additional systems and notify law enforcement.
Why this is correct
With backups encrypted and systems isolated, the team must contain the incident's spread by isolating any remaining potentially compromised systems and notify law enforcement, since ransomware is a criminal act requiring external reporting before restoration attempts.
- ✗
Reimage all systems from known clean media.
Why it's wrong here
Reimaging eradicates malware but destroys the forensic evidence needed to determine initial access and scope, so it follows evidence collection, not isolation. It is tempting because it guarantees clean systems, and would be correct once forensic imaging and root-cause analysis are complete.
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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.