SCS-C02 Threat Detection and Incident Response Practice Question
This SCS-C02 practice question tests your understanding of threat detection and incident response. 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 engineer receives an alert that an EC2 instance is generating outbound traffic to a known malicious IP address. What is the FIRST step the engineer should take as part of the incident response process?
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 EC2 instance by modifying the security group to deny all traffic.
Option C is correct because the first step in incident response for a compromised EC2 instance is containment. Modifying the security group to deny all inbound and outbound traffic immediately stops communication with the malicious IP and prevents further data exfiltration or lateral movement, while preserving the instance for forensic analysis. 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
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Analyze the network traffic logs to understand the scope.
Why it's wrong here
Analysis should occur after containment to prevent further spread.
✗
Apply the latest security patches to the EC2 instance.
Why it's wrong here
Patching is a long-term fix, not an immediate response.
✓
Isolate the EC2 instance by modifying the security group to deny all traffic.
Why this is correct
Isolation contains the threat while preserving evidence.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Terminate the EC2 instance immediately.
Why it's wrong here
Termination destroys forensic evidence.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the urgency of containment with the desire to gather evidence first, leading them to choose log analysis (Option A) instead of immediate isolation, but the exam emphasizes that containment is the priority to limit damage.
Detailed technical explanation
How to think about this question
Under the hood, modifying a security group is a stateless operation that updates the VPC's distributed firewall rules within seconds, effectively dropping all packets at the hypervisor level before they reach the instance's OS. This is preferable to using a network ACL (which is stateless and requires explicit rules for both directions) or an instance-level host firewall (which may be disabled or bypassed by a rootkit). In a real-world scenario, if the malicious IP is part of a C2 server, immediate isolation prevents the attacker from issuing further commands or exfiltrating additional data, while the engineer can later snapshot the EBS volume for offline analysis.
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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Threat Detection and Incident Response — This question tests Threat Detection and Incident Response — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Isolate the EC2 instance by modifying the security group to deny all traffic. — Option C is correct because the first step in incident response for a compromised EC2 instance is containment. Modifying the security group to deny all inbound and outbound traffic immediately stops communication with the malicious IP and prevents further data exfiltration or lateral movement, while preserving the instance for forensic analysis. This aligns with the NIST SP 800-61 incident response lifecycle, where containment precedes eradication and recovery.
What should I do if I get this SCS-C02 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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Question Discussion
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