Quick Answer
The answer is to isolate the workstation from the network. This is the correct first step because incident response first step containment prioritizes stopping the immediate threat before any other action, such as investigation or evidence collection. By disconnecting the workstation, you prevent further data exfiltration via the personal USB drive and block any potential lateral movement if the drive introduced malware, directly aligning with the containment phase of the NIST SP 800-61 lifecycle. On the CompTIA SecurityX CAS-004 exam, this scenario tests your ability to prioritize containment over eradication or recovery, a common trap where students mistakenly choose to confiscate the drive or interview the employee first. Remember, in incident response, you must contain before you collect. A simple memory tip: “Contain the pain before you explain the stain.”
This CAS-004 practice question tests your understanding of governance, risk and compliance. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 discovers that an employee has been using a personal USB drive to transfer sensitive customer data from a workstation to a home computer. This violates the company's data handling policy. According to the company's incident response plan, which of the following is the FIRST step the analyst should take?
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.
Perform a forensic analysis of the workstation
Why wrong: Forensics should follow containment to preserve evidence.
Isolate the workstation from the network
Isolation contains the incident and prevents further data transfer.
Escalate the incident to the data protection officer (DPO)
Why wrong: Escalation is important, but containment should come first.
Notify law enforcement
Why wrong: Law enforcement notification is not the first step.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Isolate the workstation from the network
The first priority in any incident response is containment to prevent further data loss or network propagation. Isolating the workstation from the network (Option B) immediately stops the employee from exfiltrating additional data and prevents any potential lateral movement by malware that might be on the USB drive. This aligns with the NIST SP 800-61 incident response lifecycle, 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
For each option: why learners choose it and why it is or isn't the right answer here.
Perform a forensic analysis of the workstation
Why it's wrong here
Forensics should follow containment to preserve evidence.
Isolate the workstation from the network
Why this is correct
Isolation contains the incident and prevents further data transfer.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Escalate the incident to the data protection officer (DPO)
Why it's wrong here
Escalation is important, but containment should come first.
Notify law enforcement
Why it's wrong here
Law enforcement notification is not the first step.
Common exam traps
CompTIA often tests the candidate's ability to prioritize containment over investigation or notification, trapping those who confuse the order of the incident response phases (e.g., jumping to forensic analysis or legal escalation before stopping the bleeding).
Detailed technical explanation
Isolation can be achieved by disabling the network interface via software (e.g., `ip link set eth0 down` on Linux, or disabling the adapter in Windows Device Manager) or by physically unplugging the Ethernet cable. In a managed environment, the analyst might also remotely quarantine the workstation using the NAC (Network Access Control) system, such as Cisco ISE, to revoke the device's access at the switch port level (802.1X CoA). This ensures the workstation cannot communicate with any network resources, including the employee's home computer via VPN or cloud services.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the CAS-004 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
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Governance, Risk and Compliance — This question tests Governance, Risk and Compliance — Read the scenario before looking for a memorised answer..
The correct answer is: Isolate the workstation from the network — The first priority in any incident response is containment to prevent further data loss or network propagation. Isolating the workstation from the network (Option B) immediately stops the employee from exfiltrating additional data and prevents any potential lateral movement by malware that might be on the USB drive. This aligns with the NIST SP 800-61 incident response lifecycle, where containment precedes eradication and recovery.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Read the scenario before looking for a memorised answer.
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Same concept, more angles
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. Refer to the exhibit. A security analyst reviews the firewall logs and sees traffic from 192.168.1.200 to the database server 10.0.0.10 on TCP port 1433. 192.168.1.200 is not in the approved IP list for database access. What is the BEST immediate action?
mediumWhy D: Blocking the source IP on the firewall immediately contains the potential threat. Investigation is important but secondary; reviewing rules is not immediate; disabling the server is too drastic.
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Last reviewed: Jun 30, 2026
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