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 is investigating a GuardDuty finding of type 'Backdoor:EC2/C&CActivity.B!DNS'. Which TWO actions should the engineer take as part of the initial response? (Choose two.)
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 its security group to deny all traffic.
Option B is correct because isolating the EC2 instance by modifying its security group to deny all traffic is a critical containment step in incident response. This immediately stops the C2 (command and control) communication detected by GuardDuty's 'Backdoor:EC2/C&CActivity.B!DNS' finding, preventing further data exfiltration or lateral movement while preserving the instance for 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.
✗
Enable Amazon GuardDuty in the account if not already enabled.
Why it's wrong here
GuardDuty is already enabled (finding exists).
✓
Isolate the EC2 instance by modifying its security group to deny all traffic.
Why this is correct
Isolation prevents further malicious activity.
Related concept
Read the scenario before looking for a memorised answer.
✗
Immediately terminate the EC2 instance to stop the activity.
Why it's wrong here
Termination destroys evidence.
✓
Take a snapshot of the instance's EBS volume for forensic analysis.
Why this is correct
Snapshot preserves evidence.
Related concept
Read the scenario before looking for a memorised answer.
✗
Disable termination protection on the instance to allow future termination.
Why it's wrong here
Does not address the threat.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse incident response containment with eradication, choosing immediate termination (Option C) instead of isolation and forensic preservation (Option B and D).
Detailed technical explanation
How to think about this question
GuardDuty's 'Backdoor:EC2/C&CActivity.B!DNS' finding specifically indicates that an EC2 instance is querying a known C2 domain via DNS. Under the hood, GuardDuty uses threat intelligence feeds and machine learning to correlate DNS query logs (from VPC Flow Logs or Route 53 Resolver) with known malicious domains. Isolating via security group is preferred over network ACLs because security groups are stateful and can block all traffic immediately without affecting the instance's metadata or termination state, allowing for live forensics or memory capture.
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 its security group to deny all traffic. — Option B is correct because isolating the EC2 instance by modifying its security group to deny all traffic is a critical containment step in incident response. This immediately stops the C2 (command and control) communication detected by GuardDuty's 'Backdoor:EC2/C&CActivity.B!DNS' finding, preventing further data exfiltration or lateral movement while preserving the instance for forensic analysis.
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.
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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