SCS-C02 Security Logging and Monitoring Practice Question
This SCS-C02 practice question tests your understanding of security logging and monitoring. 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 engineer is troubleshooting an issue where CloudTrail logs for a single AWS account are not being delivered to the centralized S3 bucket in the logging account. The engineer has verified that the CloudTrail trail is enabled, the S3 bucket policy allows CloudTrail to write, and the bucket exists. However, no log files have been delivered for the past 6 hours. The engineer checks the CloudTrail console and sees that the trail status shows 'Logging' but the latest log file time is from 8 hours ago. The engineer suspects a permission issue but cannot find any explicit deny in the bucket policy. What is the MOST likely cause of this issue?
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 KMS key policy used by the S3 bucket does not grant CloudTrail permission to use the key.
The issue is likely that the KMS key used for server-side encryption of the S3 bucket is not configured to allow CloudTrail to decrypt logs. CloudTrail requires decrypt permission on the KMS key to write logs, even if the trail uses SSE-S3 for the log files themselves. The bucket policy may allow CloudTrail to write, but if the KMS key policy does not grant kms:Decrypt to the CloudTrail service principal, log delivery will fail. Option A is correct because the KMS key policy likely needs a statement allowing CloudTrail to use the key. Option B is wrong because CloudTrail does not need S3 full access, only write access. Option C is wrong because the bucket exists and is accessible. Option D is wrong because CloudTrail can deliver to a bucket in another account with proper permissions.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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 CloudTrail trail is not configured to deliver to a cross-account bucket.
Why it's wrong here
CloudTrail supports cross-account delivery with proper bucket policies.
✗
The CloudTrail trail is configured with a role that does not have S3 full access.
Why it's wrong here
CloudTrail does not require S3 full access; write permission is sufficient.
✗
The S3 bucket is in a different region than the CloudTrail trail.
Why it's wrong here
CloudTrail can deliver to a bucket in any region.
✓
The KMS key policy used by the S3 bucket does not grant CloudTrail permission to use the key.
Why this is correct
CloudTrail needs kms:Decrypt permission on the KMS key to write to SSE-KMS encrypted buckets.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related SCS-C02 ACL questions on filtering logic and placement.
Security Logging and Monitoring — This question tests Security Logging and Monitoring — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: The KMS key policy used by the S3 bucket does not grant CloudTrail permission to use the key. — The issue is likely that the KMS key used for server-side encryption of the S3 bucket is not configured to allow CloudTrail to decrypt logs. CloudTrail requires decrypt permission on the KMS key to write logs, even if the trail uses SSE-S3 for the log files themselves. The bucket policy may allow CloudTrail to write, but if the KMS key policy does not grant kms:Decrypt to the CloudTrail service principal, log delivery will fail. Option A is correct because the KMS key policy likely needs a statement allowing CloudTrail to use the key. Option B is wrong because CloudTrail does not need S3 full access, only write access. Option C is wrong because the bucket exists and is accessible. Option D is wrong because CloudTrail can deliver to a bucket in another account with proper permissions.
What should I do if I get this SCS-C02 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related SCS-C02 ACL questions on filtering logic and placement.
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?
Standard ACLs match source addresses.
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