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.
You are a senior security analyst at a mid-sized financial company. The SOC has been alerted by the EDR system about anomalous behavior on a domain controller (DC) that runs Windows Server 2019. The alert indicates that a process named 'svchost.exe' spawned a PowerShell process that executed a one-liner to connect to an external IP address (203.0.113.5) over TCP port 443. Further investigation shows that the DC's event logs have gaps of about 10 minutes each, and the local administrator account 'Administrator' was used to log in from a workstation named 'WKSTN-FIN-12' at the time of the event. The company has strict policies: all administrative access must be via dedicated jump hosts, and privileged accounts are monitored. Upon checking, 'WKSTN-FIN-12' is assigned to an employee in the finance department who has no administrative privileges. The employee reports that they did not log in recently. The CISO wants a swift containment and eradication without losing forensic evidence. Based on this scenario, which of the following is the BEST first course of action?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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 domain controller from the network by disabling its network interface.
Isolating the domain controller by disabling its network interface is the best first step because it immediately halts any ongoing malicious communication (e.g., C2 traffic over TCP 443) while preserving the volatile state of the system for forensic acquisition. This action prevents further data exfiltration or lateral movement without destroying evidence like memory or logs, which would occur with a power-down. It also aligns with the CISO's requirement for swift containment without losing forensic evidence.
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 domain controller from the network by disabling its network interface.
Why this is correct
Isolation contains the threat while preserving evidence for analysis.
Clue confirmation
The clue words "best", "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Capture a memory dump of the domain controller for offline analysis.
Why it's wrong here
Memory capture is important but should be done after isolation to prevent ongoing damage.
✗
Power down the domain controller to prevent further damage.
Why it's wrong here
Powering down loses volatile data and is not best practice before forensic acquisition.
✗
Reset the password for the local Administrator account and revoke the user's access.
Why it's wrong here
Resetting may tip off the attacker and does not isolate the DC.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the distinction between containment and forensic preservation, trapping candidates who choose memory capture (Option B) as a first step instead of immediate isolation, or who mistakenly think powering down (Option C) preserves evidence when it actually destroys volatile data.
Detailed technical explanation
How to think about this question
Disabling the network interface (e.g., via `netsh interface set interface name='Ethernet' admin=disable` or through the Hyper-V/VMware console) stops all Layer 2/3 traffic, cutting the C2 channel without triggering process termination or disk writes that could alter evidence. This preserves the process memory, network state, and event logs for later analysis using tools like Volatility or FTK Imager. In real-world incidents, this approach is preferred over unplugging the cable because it can be done remotely and avoids physical access delays.
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 SOC analyst notices unusual lateral movement in the network at 2 AM. The IR playbook dictates: identify and contain (isolate the affected machine), then eradicate (remove the malware), then recover (restore from backup), then document. Skipping containment before eradication risks the attacker regaining access. Questions like this test the sequence and rationale of incident response phases.
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: Isolate the domain controller from the network by disabling its network interface. — Isolating the domain controller by disabling its network interface is the best first step because it immediately halts any ongoing malicious communication (e.g., C2 traffic over TCP 443) while preserving the volatile state of the system for forensic acquisition. This action prevents further data exfiltration or lateral movement without destroying evidence like memory or logs, which would occur with a power-down. It also aligns with the CISO's requirement for swift containment without losing forensic evidence.
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.
Are there clue words in this question I should notice?
Yes — watch for: "best", "first". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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