This CC practice question tests your understanding of security operations. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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.
You are a SOC analyst for a financial institution. At 2:00 AM, your SIEM generates a critical alert from the email security gateway indicating that an internal user received a phishing email with a malicious attachment. The email was delivered to the user's inbox, and the user's account activity logs show that the attachment was opened 10 minutes ago. The user is a junior accountant who works in the accounts payable department. You have access to endpoint detection tools, email logs, and network traffic data. The organization's incident response policy requires containment within 30 minutes of detection. Which action should you take 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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Isolate the user's workstation from the network to prevent lateral movement.
The incident response policy requires containment within 30 minutes. Isolating the workstation (e.g., via network access control or disabling the switch port) immediately stops any ongoing malicious activity, such as command-and-control communication or lateral movement, which is the highest priority after detection. This aligns with the NIST SP 800-61 containment strategy and the SANS PICERL model, where containment precedes eradication and recovery.
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.
✓
Isolate the user's workstation from the network to prevent lateral movement.
Why this is correct
Isolation contains the incident quickly, as per policy.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Scan the user's workstation with antivirus software.
Why it's wrong here
Scanning is analysis, not containment, and may miss advanced malware.
✗
Block the sender's email address at the email gateway.
Why it's wrong here
This prevents future emails but does not address the already-opened attachment.
✗
Send an email to the user instructing them to delete the email.
Why it's wrong here
This is not immediate containment; the user may not see the email or may not act promptly.
Common exam traps
Common exam trap: answer the scenario, not the keyword
ISC2 often tests the principle that containment must happen before any eradication or recovery steps, so candidates mistakenly choose scanning or blocking the sender because they focus on the email vector rather than the active compromise on the endpoint.
Detailed technical explanation
How to think about this question
Network isolation can be achieved by disabling the switch port (via SNMP or CLI), applying a host-based firewall rule to drop all traffic except to the SIEM/management subnet, or using an EDR's built-in isolation feature that blocks all outbound connections at the kernel level. In a real-world scenario, failing to isolate quickly allowed the NotPetya worm to spread from a single accounting workstation to the entire enterprise within minutes via SMB and PsExec.
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
An employee at a financial services firm receives an email that appears to come from the IT helpdesk, asking them to reset their password via a link. The link leads to a convincing fake portal that harvests credentials. Security teams use phishing simulations and security-awareness training to reduce this attack vector. Questions like this test whether you can identify social engineering techniques and appropriate controls.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CC 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: Isolate the user's workstation from the network to prevent lateral movement. — The incident response policy requires containment within 30 minutes. Isolating the workstation (e.g., via network access control or disabling the switch port) immediately stops any ongoing malicious activity, such as command-and-control communication or lateral movement, which is the highest priority after detection. This aligns with the NIST SP 800-61 containment strategy and the SANS PICERL model, where containment precedes eradication and recovery.
What should I do if I get this CC 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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