This CS0-003 practice question tests your understanding of security operations. 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.
A security team is reviewing firewall logs and identifies traffic to a known malicious IP address from an internal workstation running a critical business application that cannot be interrupted. Which of the following is the most appropriate immediate action?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add a firewall rule to block the malicious IP
Adding a firewall rule to block the malicious IP is the most appropriate immediate action because it stops the outbound traffic to the known malicious address without disrupting the critical business application running on the workstation. This approach maintains availability (a key CIA triad principle) while mitigating the threat at the network layer, which is faster and less invasive than host-level changes. It also preserves the workstation's state for potential forensic analysis.
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.
✓
Add a firewall rule to block the malicious IP
Why this is correct
Blocking just the malicious IP minimizes disruption while preventing further communication.
Related concept
Read the scenario before looking for a memorised answer.
✗
Shut down the workstation
Why it's wrong here
Shutting down would interrupt the critical business application.
✗
Disconnect the network cable
Why it's wrong here
Disconnecting the cable would also disrupt the application.
✗
Run an antivirus scan
Why it's wrong here
Running an antivirus scan is not an immediate containment action and may not stop ongoing communication.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the principle of 'least disruption' in incident response, where candidates mistakenly choose to shut down or disconnect the system (options B or C) because they focus solely on containment, forgetting the critical business application's availability requirement.
Detailed technical explanation
How to think about this question
A firewall rule blocking a specific IP uses an access control list (ACL) entry that matches the destination IP address and drops packets at Layer 3, typically before stateful inspection. In a real-world scenario, the security team might use a next-generation firewall (NGFW) with application-layer awareness to create a rule that blocks only traffic to the malicious IP while allowing all other traffic for the critical application. This approach also preserves the ability to later analyze the workstation's outbound connections via firewall logs without altering the host's state.
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 developer is choosing between AES-256 (symmetric) and RSA-2048 (asymmetric) for encrypting a large file that will be sent to a partner. Symmetric encryption is fast but requires key exchange; asymmetric is slower but solves the key distribution problem. A hybrid approach — encrypt the file with AES, encrypt the AES key with RSA — is standard. Questions like this test whether you understand when each approach applies.
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: Add a firewall rule to block the malicious IP — Adding a firewall rule to block the malicious IP is the most appropriate immediate action because it stops the outbound traffic to the known malicious address without disrupting the critical business application running on the workstation. This approach maintains availability (a key CIA triad principle) while mitigating the threat at the network layer, which is faster and less invasive than host-level changes. It also preserves the workstation's state for potential forensic analysis.
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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