This CS0-003 practice question tests your understanding of security operations. 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 security analyst is reviewing logs from a network intrusion detection system (NIDS) and sees the following alert: "ET TROJAN Possible ZeuS/Poison Ivy Activity". The analyst wants to verify if the traffic is malicious. Which TWO of the following actions should the analyst take? (Select two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Check the source IP against threat intelligence feeds.
Option C is correct because checking the source IP against threat intelligence feeds (e.g., AlienVault OTX, VirusTotal, or commercial feeds) allows the analyst to determine if the IP is known for hosting ZeuS/Poison Ivy command-and-control (C2) infrastructure. This action directly validates whether the alert corresponds to a known malicious entity, reducing reliance on signature-based detection alone.
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.
✗
Disable the NIDS signature to prevent false positives.
Why it's wrong here
Ignores future alerts, not a verification step.
✗
Perform a packet capture of the session for further analysis.
Why it's wrong here
Useful but not among the two best immediate verification steps.
✓
Check the source IP against threat intelligence feeds.
Why this is correct
Helps confirm if the source is known malicious.
Related concept
Read the scenario before looking for a memorised answer.
✗
Restart the NIDS service.
Why it's wrong here
Disrupts monitoring and does not help verify.
✓
Correlate the alert with other logs (e.g., firewall, proxy).
Why this is correct
Provides context to validate the alert.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between reactive analysis (packet capture) and proactive verification (threat intelligence correlation), trapping candidates who think packet capture is the first step instead of a follow-up action.
Detailed technical explanation
How to think about this question
ZeuS and Poison Ivy typically use encrypted C2 channels over HTTP or HTTPS, making signature-based detection prone to false positives when benign traffic mimics their patterns (e.g., User-Agent strings or URI structures). Threat intelligence feeds aggregate data from sinkholes, sandboxes, and global telemetry to provide reputation scores for IPs, domains, and hashes, enabling analysts to prioritize alerts with high confidence. Correlating with firewall logs (option E) can reveal additional context like connection duration, data volume, or outbound port usage, which helps distinguish a true C2 beacon from a legitimate web request.
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 security analyst at a medium-sized enterprise encounters this scenario during an investigation or architecture review. The correct answer reflects best practice for the specific threat or control described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CS0-003 question in full detail.
Security Operations — This question tests Security Operations — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Check the source IP against threat intelligence feeds. — Option C is correct because checking the source IP against threat intelligence feeds (e.g., AlienVault OTX, VirusTotal, or commercial feeds) allows the analyst to determine if the IP is known for hosting ZeuS/Poison Ivy command-and-control (C2) infrastructure. This action directly validates whether the alert corresponds to a known malicious entity, reducing reliance on signature-based detection alone.
What should I do if I get this CS0-003 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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