Isolate the host for investigation is the correct first action because when threat intelligence indicates command-and-control (C2) traffic, the priority is immediate containment to sever the attacker’s communication channel and prevent further data exfiltration or lateral movement. This step aligns with the NIST incident response framework’s containment phase, which must precede any deep forensic analysis or evidence gathering. On the Certified Information Security Manager CISM exam, this scenario tests your understanding of the incident response lifecycle and the critical distinction between containment and investigation—a common trap is jumping to log review or threat hunting before stopping the active threat. Remember the memory tip: “C2 means cut the cord first,” reinforcing that isolation halts the attacker’s control before you dig into the details.
CISM Incident Management Practice Question
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.
Exhibit
Refer to the exhibit.
[Threat Intelligence Feed]
Indicator: 203.0.113.5
Type: IP
Confidence: High
Tags: C2, Malware
[Proxy Log]
src=10.0.1.50 dst=203.0.113.5 port=443 action=ALLOWED
The SIEM alerts on this traffic. What should the incident analyst do FIRST?
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.
Refer to the exhibit.
[Threat Intelligence Feed]
Indicator: 203.0.113.5
Type: IP
Confidence: High
Tags: C2, Malware
[Proxy Log]
src=10.0.1.50 dst=203.0.113.5 port=443 action=ALLOWED
A
Isolate the host for investigation.
Option C is correct because the threat intelligence suggests C2, so isolating the host prevents further potential data loss or lateral movement while investigation proceeds.
B
Accept the traffic as normal.
Why wrong: Option D is incorrect.
C
Block the IP at the firewall.
Why wrong: Option A is possible but first step should be containment via isolation.
D
Check if the destination is a legitimate CDN.
Why wrong: Option B is worth checking but not first.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Isolate the host for investigation.
Option C is correct because the threat intelligence suggests C2, so isolating the host prevents further potential data loss or lateral movement while investigation proceeds. Option A is possible but first step should be containment via isolation. Option B is worth checking but not first. Option D is incorrect.
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
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Isolate the host for investigation.
Why this is correct
Option C is correct because the threat intelligence suggests C2, so isolating the host prevents further potential data loss or lateral movement while investigation proceeds.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
Accept the traffic as normal.
Why it's wrong here
Option D is incorrect.
✗
Block the IP at the firewall.
Why it's wrong here
Option A is possible but first step should be containment via isolation.
✗
Check if the destination is a legitimate CDN.
Why it's wrong here
Option B is worth checking but not first.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
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
How to think about this question
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.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
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
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.
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.
Incident Management — This question tests Incident Management — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Isolate the host for investigation. — Option C is correct because the threat intelligence suggests C2, so isolating the host prevents further potential data loss or lateral movement while investigation proceeds. Option A is possible but first step should be containment via isolation. Option B is worth checking but not first. Option D is incorrect.
What should I do if I get this CISM question wrong?
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.
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?
Static NAT maps one inside address to one outside address.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A security analyst receives an alert from the SIEM indicating a high number of failed login attempts from a single external IP address targeting a public-facing web server. The analyst checks the logs and sees that the attempts are using common usernames. What is the MOST appropriate immediate response?
easy
✓ A.Block the IP address at the firewall.
B.Ignore the alert as it is likely a false positive.
C.Disable the web server.
D.Notify law enforcement.
Why A: Option A is correct because blocking the IP at the firewall is a quick containment measure to stop the attack. Option B is wrong because ignoring could lead to successful brute-force. Option C is premature as law enforcement is not needed at this stage. Option D is too drastic and would disrupt business.
Variation 2. A security analyst detects a potential data exfiltration from a critical server. According to incident response best practices, what is the first action the analyst should take?
easy
✓ A.Disconnect the server from the network immediately.
B.Notify the incident response manager.
C.Review firewall logs to confirm the exfiltration.
D.Take a forensic image of the server.
Why A: Option A is correct because immediate containment is the priority to stop further data loss. Other actions are important but should follow containment.
Last reviewed: Jun 24, 2026
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.