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.
A multinational corporation has just detected a ransomware attack that encrypted critical files on a file server. The incident response team has been activated. Which of the following should be the FIRST action taken by the team?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Isolate the affected systems from the network
The first priority in ransomware incident response is containment to prevent the encryption from spreading to other systems. Isolating the affected file server from the network (e.g., disabling the network interface or disconnecting the cable) stops the ransomware from communicating with its command-and-control server and encrypting additional shares. This aligns with the NIST SP 800-61 containment strategy and ensures that the incident response team can safely preserve forensic evidence before any remediation.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Restore encrypted files from backup
Why it's wrong here
Restoration should occur after containment and forensic analysis.
✗
Reboot the file server to clear the encryption
Why it's wrong here
Rebooting may lose volatile evidence and does not remove encryption.
✓
Isolate the affected systems from the network
Why this is correct
Isolation stops the ransomware from spreading and limits damage.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Notify law enforcement
Why it's wrong here
Notifying law enforcement is important but not the first step; containment is priority.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose 'Restore from backup' first because it seems like a direct fix, but CISM emphasizes containment before eradication or recovery to limit damage and preserve forensic integrity.
Detailed technical explanation
How to think about this question
Ransomware typically uses a hybrid encryption scheme: a symmetric key (e.g., AES-256) encrypts files quickly, and that key is then encrypted with an asymmetric public key (e.g., RSA-2048) from the attacker's C2 server. Isolating the system cuts off the C2 communication, preventing the attacker from exfiltrating data or delivering additional payloads. In a real-world scenario, a file server may host multiple SMB shares; network isolation (e.g., disabling the NIC via `ifconfig down` or `netsh interface set interface name="Ethernet" admin=disable`) stops lateral movement to domain controllers or backup servers.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
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
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Incident Management — This question tests Incident Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Isolate the affected systems from the network — The first priority in ransomware incident response is containment to prevent the encryption from spreading to other systems. Isolating the affected file server from the network (e.g., disabling the network interface or disconnecting the cable) stops the ransomware from communicating with its command-and-control server and encrypting additional shares. This aligns with the NIST SP 800-61 containment strategy and ensures that the incident response team can safely preserve forensic evidence before any remediation.
What should I do if I get this CISM question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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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.
Question Discussion
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