The correct answer is the bucket policy statement that grants the CloudTrail service principal the kms:Decrypt action on the KMS key. This is because when you encrypt CloudTrail logs with a KMS customer managed key, the CloudTrail service itself must be explicitly allowed to decrypt the logs during delivery to the S3 bucket; the key policy controls who can use the key, but the bucket policy must authorize the service principal to perform the decrypt operation. On the AWS Certified Security Specialty SCS-C02 exam, this question tests your understanding of the separation between key policies and bucket policies, and a common trap is confusing the root user or wildcard principals with the specific cloudtrail.amazonaws.com service principal. Remember the memory tip: “CloudTrail decrypts, not the root or the world—only the service principal is unfurled.”
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 security engineer is configuring an Amazon S3 bucket to store CloudTrail logs. The engineer must ensure that the logs are encrypted at rest using an AWS KMS customer managed key (CMK) and that only the CloudTrail service has permission to decrypt the logs. Which bucket policy statement should the engineer add?
Option A is correct because it grants the CloudTrail service principal the necessary decrypt permission. Option B is wrong because the root user is not the CloudTrail service. Option C is wrong because it grants decrypt to all principals, which is too permissive. Option D is wrong because the CMK key policy, not bucket policy, controls KMS permissions.
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.
This grants the root user decrypt permission, not CloudTrail service.
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: {"Effect":"Allow","Principal":{"Service":"cloudtrail.amazonaws.com"},"Action":"kms:Decrypt","Resource":"*"} — Option A is correct because it grants the CloudTrail service principal the necessary decrypt permission. Option B is wrong because the root user is not the CloudTrail service. Option C is wrong because it grants decrypt to all principals, which is too permissive. Option D is wrong because the CMK key policy, not bucket policy, controls KMS permissions.
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.
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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