SCS-C02 Threat Detection and Incident Response Practice Question
This SCS-C02 practice question tests your understanding of threat detection and incident response. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 company runs a critical web application on Amazon EC2 instances behind an Application Load Balancer (ALB) in a VPC. The security team uses Amazon GuardDuty and has enabled Amazon Detective. Recently, GuardDuty raised a 'Recon:EC2/PortProbeUnprotectedPort' finding for one of the instances. The security engineer verified that the ALB security group only allows inbound HTTP/HTTPS from the internet. However, the finding indicates that the instance is receiving probes on port 22 (SSH). Further investigation with Detective shows that the probes originate from multiple IP addresses and are reaching the instance's private IP address. The engineer suspects that the SSH port is exposed despite the security group configuration. What is the MOST likely cause of this exposure?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The EC2 instance's security group allows inbound SSH from 0.0.0.0/0.
The GuardDuty finding 'Recon:EC2/PortProbeUnprotectedPort' indicates that an EC2 instance is receiving unsolicited probes on a port that should not be publicly accessible. Since the ALB security group only allows HTTP/HTTPS from the internet, but the probes are reaching the instance's private IP on port 22 (SSH), the most likely cause is that the instance's own security group has an inbound rule allowing SSH from 0.0.0.0/0. This bypasses the ALB's security group because the instance's security group is evaluated independently for direct traffic to the instance's private IP, and if it permits SSH from anywhere, the probes will reach the 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.
✓
The EC2 instance's security group allows inbound SSH from 0.0.0.0/0.
Why this is correct
If the instance's security group allows SSH from anywhere, the instance is exposed even if behind an ALB.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
VPC Flow Logs are misconfigured and are inadvertently forwarding traffic to the instance.
Why it's wrong here
VPC Flow Logs capture metadata but do not affect network traffic.
✗
AWS Shield Advanced is causing false positives by marking legitimate traffic as probes.
Why it's wrong here
Shield Advanced does not cause false positives in GuardDuty findings; it provides DDoS protection.
✗
The ALB security group has an inbound rule that allows SSH from the internet.
Why it's wrong here
The engineer verified that the ALB security group only allows HTTP/HTTPS, so this is not the cause.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume the ALB's security group fully protects the backend instances, forgetting that instances have their own security groups that are evaluated independently for direct traffic to their private IPs.
Detailed technical explanation
How to think about this question
In a VPC, security groups act as a stateful firewall at the instance level. When traffic reaches an instance's private IP directly (not via the ALB), the instance's own security group rules are evaluated, not the ALB's. The ALB only forwards traffic to instances on the listener ports (e.g., 80/443) and does not alter the source IP or bypass instance security groups. This is a common misconfiguration where engineers assume the ALB's security group protects the instance from all inbound traffic, but the instance's security group must also be restrictive.
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: The EC2 instance's security group allows inbound SSH from 0.0.0.0/0. — The GuardDuty finding 'Recon:EC2/PortProbeUnprotectedPort' indicates that an EC2 instance is receiving unsolicited probes on a port that should not be publicly accessible. Since the ALB security group only allows HTTP/HTTPS from the internet, but the probes are reaching the instance's private IP on port 22 (SSH), the most likely cause is that the instance's own security group has an inbound rule allowing SSH from 0.0.0.0/0. This bypasses the ALB's security group because the instance's security group is evaluated independently for direct traffic to the instance's private IP, and if it permits SSH from anywhere, the probes will reach the 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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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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