- A
Configure the S3 bucket to use SSE-KMS encryption with the customer-managed key, and modify the KMS key policy to grant the kms:Decrypt permission only to the 'Auditors' role.
This is correct. SSE-KMS encrypts objects at rest using a KMS key. The KMS key policy controls who can use the key to decrypt objects. By restricting kms:Decrypt to the 'Auditors' role, only that role can decrypt the objects, regardless of broader S3 read permissions.
- B
Configure an S3 bucket policy that denies s3:GetObject requests unless the request is encrypted in transit using HTTPS.
Why wrong: This enforces HTTPS for all requests but does not prevent unauthorized decryption of objects. A user who has s3:GetObject permission via the bucket policy can still download the encrypted object, and if they have kms:Decrypt permission, they could decrypt it. This option does not address the requirement to restrict decryption.
- C
Enable S3 Block Public Access on the bucket and attach an IAM policy to the 'Auditors' role that allows s3:GetObject.
Why wrong: Block Public Access and IAM policies control who can read the objects from S3, but they do not control who can decrypt objects encrypted with a KMS key. Any principal with s3:GetObject permission could download the encrypted object; the KMS key policy then determines if they can decrypt it. This option does not restrict decryption to only the 'Auditors' role.
- D
Use S3 object-level logging to monitor access and revoke permissions for any role that attempts to decrypt objects without authorization.
Why wrong: This is a reactive, detective control, not a preventive one. It does not enforce that only the 'Auditors' role can decrypt objects. Unauthorized decryption could occur before revocation. The requirement is to enforce access control, not just monitor it.
Quick Answer
The correct answer is to configure the S3 bucket with SSE-KMS using the customer-managed key and modify the KMS key policy to grant kms:Decrypt only to the 'Auditors' IAM role. This works because AWS KMS key policies act as the definitive access control for decryption operations, overriding broader S3 bucket policies that allow s3:GetObject. Even if other users can read the encrypted object from S3, they cannot decrypt it without explicit kms:Decrypt permission on the key, enforcing a strict separation between read access and decryption access. On the AWS Certified Cloud Practitioner CLF-C02 exam, this scenario tests your understanding of how KMS key policies can restrict decrypt actions independently of S3 policies—a common trap is assuming the S3 bucket policy alone controls decryption. Remember the memory tip: "S3 gives you the box, but KMS holds the key; only the role with the key policy can open it."
CLF-C02 Security and Compliance Practice Question
This CLF-C02 practice question tests your understanding of security and compliance. 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 company stores sensitive financial reports in an Amazon S3 bucket. The company's security policy mandates that all objects be encrypted at rest using an AWS KMS customer-managed key. The security team wants to ensure that only the 'Auditors' IAM role can decrypt the objects, even though the S3 bucket policy allows read access to a broader set of users. Which of the following steps must the security team take to enforce this access control?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Configure the S3 bucket to use SSE-KMS encryption with the customer-managed key, and modify the KMS key policy to grant the kms:Decrypt permission only to the 'Auditors' role.
Option A is correct because SSE-KMS with a customer-managed key separates encryption key management from S3 bucket policies. The KMS key policy is the authoritative access control for decryption operations. By granting kms:Decrypt only to the 'Auditors' role, even if the S3 bucket policy allows s3:GetObject to other users, they cannot decrypt the objects without the key permission. This enforces the security requirement that only the Auditors role can decrypt the sensitive financial reports.
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.
- ✓
Configure the S3 bucket to use SSE-KMS encryption with the customer-managed key, and modify the KMS key policy to grant the kms:Decrypt permission only to the 'Auditors' role.
Why this is correct
This is correct. SSE-KMS encrypts objects at rest using a KMS key. The KMS key policy controls who can use the key to decrypt objects. By restricting kms:Decrypt to the 'Auditors' role, only that role can decrypt the objects, regardless of broader S3 read permissions.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Configure an S3 bucket policy that denies s3:GetObject requests unless the request is encrypted in transit using HTTPS.
Why it's wrong here
This enforces HTTPS for all requests but does not prevent unauthorized decryption of objects. A user who has s3:GetObject permission via the bucket policy can still download the encrypted object, and if they have kms:Decrypt permission, they could decrypt it. This option does not address the requirement to restrict decryption.
- ✗
Enable S3 Block Public Access on the bucket and attach an IAM policy to the 'Auditors' role that allows s3:GetObject.
Why it's wrong here
Block Public Access and IAM policies control who can read the objects from S3, but they do not control who can decrypt objects encrypted with a KMS key. Any principal with s3:GetObject permission could download the encrypted object; the KMS key policy then determines if they can decrypt it. This option does not restrict decryption to only the 'Auditors' role.
- ✗
Use S3 object-level logging to monitor access and revoke permissions for any role that attempts to decrypt objects without authorization.
Why it's wrong here
This is a reactive, detective control, not a preventive one. It does not enforce that only the 'Auditors' role can decrypt objects. Unauthorized decryption could occur before revocation. The requirement is to enforce access control, not just monitor it.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume S3 bucket policies alone can control decryption, but AWS enforces KMS key policies as a separate authorization layer, so without explicitly restricting kms:Decrypt in the key policy, any user with s3:GetObject can decrypt the objects if they have KMS permissions through their IAM role or user.
Detailed technical explanation
How to think about this question
Under the hood, when SSE-KMS is used, S3 sends a GenerateDataKey request to KMS during upload and a Decrypt request during download. The KMS key policy is evaluated separately from S3 bucket policies; an IAM principal must have both s3:GetObject (from S3 policy) and kms:Decrypt (from KMS key policy) to successfully read and decrypt an object. This dual-authorization model is a common pattern for enforcing least privilege in multi-account or cross-team scenarios, such as when a data lake bucket is shared but only a specific security team can decrypt sensitive columns.
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 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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this CLF-C02 question test?
Security and Compliance — This question tests Security and Compliance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure the S3 bucket to use SSE-KMS encryption with the customer-managed key, and modify the KMS key policy to grant the kms:Decrypt permission only to the 'Auditors' role. — Option A is correct because SSE-KMS with a customer-managed key separates encryption key management from S3 bucket policies. The KMS key policy is the authoritative access control for decryption operations. By granting kms:Decrypt only to the 'Auditors' role, even if the S3 bucket policy allows s3:GetObject to other users, they cannot decrypt the objects without the key permission. This enforces the security requirement that only the Auditors role can decrypt the sensitive financial reports.
What should I do if I get this CLF-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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Last reviewed: Jun 11, 2026
This CLF-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CLF-C02 exam.
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