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 discovers an Amazon GuardDuty finding of type 'UnauthorizedAccess:EC2/SSHBruteForce' for an EC2 instance. The instance is part of an Auto Scaling group and has a public IP address. What is the MOST effective immediate step to mitigate the threat?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Detach the instance from the Auto Scaling group and terminate it.
Option D is correct because the instance is compromised and part of an Auto Scaling group. Detaching it first prevents the Auto Scaling group from immediately replacing it with a new instance that might inherit the same vulnerability, allowing for forensic analysis. Terminating it after detachment stops the SSH brute force attack at its source without risking automatic re-provisioning of a similarly exposed instance.
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.
✗
Modify the network ACL to block SSH traffic from the attacker's IP.
Why it's wrong here
NACLs are stateless and can block traffic, but the instance remains running and may have been compromised.
✗
Terminate the instance without detaching it from the Auto Scaling group.
Why it's wrong here
The Auto Scaling group will immediately launch a replacement instance, which may also be vulnerable.
✗
Update the security group to restrict SSH access to known IP addresses.
Why it's wrong here
While this is a good practice, it does not immediately stop an ongoing attack if the instance is already under brute force.
✓
Detach the instance from the Auto Scaling group and terminate it.
Why this is correct
This stops the attack and prevents the Auto Scaling group from automatically launching a new instance.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume terminating the instance directly (Option B) is sufficient, failing to recognize that Auto Scaling groups automatically replace terminated instances, which can immediately re-expose the environment to the same threat.
Detailed technical explanation
How to think about this question
Under the hood, Amazon GuardDuty analyzes VPC Flow Logs, DNS logs, and CloudTrail events to detect SSH brute force patterns. When an instance is part of an Auto Scaling group, the group's desired capacity is maintained automatically; terminating an instance without detaching it first causes the Auto Scaling group to launch a new instance from the launch template or configuration, which may have the same public IP and security group rules, perpetuating the attack surface. Detachment decouples the instance from the group's lifecycle management, allowing the security engineer to investigate and remediate without triggering automatic replacement.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
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: Detach the instance from the Auto Scaling group and terminate it. — Option D is correct because the instance is compromised and part of an Auto Scaling group. Detaching it first prevents the Auto Scaling group from immediately replacing it with a new instance that might inherit the same vulnerability, allowing for forensic analysis. Terminating it after detachment stops the SSH brute force attack at its source without risking automatic re-provisioning of a similarly exposed instance.
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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