The answer is that the KMS key policy does not grant the engineer’s role permission to decrypt. When troubleshooting CloudTrail logs SSE-KMS access denied errors, the most common cause is that the KMS key policy lacks a statement allowing the IAM role to perform kms:Decrypt, even when the user has s3:GetObject on the bucket. SSE-KMS requires two separate permissions: S3 read access and KMS decrypt access; the error occurs because the S3 service cannot decrypt the object on the user’s behalf without the key policy granting that permission. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of the layered permission model between S3 and KMS, often appearing as a trap where candidates mistakenly blame S3 bucket policies or IAM roles. A key memory tip is “S3 opens the door, KMS unlocks the box”—without decrypt permission on the key policy, the box stays locked regardless of S3 access.
SCS-C02 Security Logging and Monitoring Practice Question
This SCS-C02 practice question tests your understanding of security logging and monitoring. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 financial services company uses AWS CloudTrail to log all API calls in their account. They store the logs in an S3 bucket with server-side encryption using AWS KMS (SSE-KMS). The security team needs to ensure that only authorized users can decrypt and read the logs. They have created a KMS key with a key policy that grants decrypt permissions to the security team's IAM roles. However, when a security engineer tries to download a log file from the S3 bucket using the AWS CLI, they receive an 'AccessDenied' error. The engineer has s3:GetObject permission on the bucket. What is the most likely cause?
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 does not grant the engineer's role permission to decrypt.
Option C is correct because the KMS key policy must grant the engineer's role kms:Decrypt permission. Option A is wrong because the error is not about S3 permissions. Option B is wrong because S3 bucket policy does not control KMS permissions. Option D is wrong because CloudTrail does not need decrypt permission for reading logs.
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 CloudTrail trail is not configured to use SSE-KMS.
Why it's wrong here
The trail is configured, but that does not affect read access.
✗
The S3 bucket has a bucket policy that denies access to the engineer's IAM role.
Why it's wrong here
No indication of explicit deny.
✗
The S3 bucket policy does not allow the engineer to read objects.
Why it's wrong here
The engineer has s3:GetObject permission, so S3 bucket policy is not the issue.
✓
The KMS key policy does not grant the engineer's role permission to decrypt.
Why this is correct
The engineer needs kms:Decrypt permission on the KMS key to read encrypted objects.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 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.
Identify which SCS-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Security Logging and Monitoring — This question tests Security Logging and Monitoring — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The KMS key policy does not grant the engineer's role permission to decrypt. — Option C is correct because the KMS key policy must grant the engineer's role kms:Decrypt permission. Option A is wrong because the error is not about S3 permissions. Option B is wrong because S3 bucket policy does not control KMS permissions. Option D is wrong because CloudTrail does not need decrypt permission for reading logs.
What should I do if I get this SCS-C02 question wrong?
Identify which SCS-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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