- A
Modify the bucket policy to use a Deny effect with a condition on the s3:x-amz-server-side-encryption-aws-kms-key-id header being null, and also enable S3 default encryption with the custom KMS key so that objects uploaded without explicit headers are automatically encrypted with the correct key.
Correct: Default encryption catches objects without headers, and the bucket policy denies explicit mismatches, enforcing both backward compatibility and compliance.
- B
Implement AWS Config rules to detect non-compliant objects and automatically re-encrypt them with the correct key, while keeping the bucket policy unchanged.
Why wrong: Incorrect: This is a corrective measure after the fact, not preventative; the bucket policy would still block scripts that omit headers.
- C
Remove the bucket policy and rely solely on S3 default encryption with the custom KMS key, because default encryption applies to all objects.
Why wrong: Incorrect: Default encryption encrypts objects but does not prevent the development team from overriding the encryption with a non-compliant key if they explicitly set headers.
- D
Create a new S3 bucket with the required policy and migrate all data using AWS DataSync, then delete the old bucket.
Why wrong: Incorrect: This adds complexity and migration time without addressing the immediate issue of failing uploads in the current bucket.
CCSP Cloud Data Security Practice Question
This CCSP practice question tests your understanding of cloud data security. 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 healthcare organization is migrating to AWS and must protect electronic protected health information (ePHI) stored in S3. They use AWS KMS with a custom key policy that restricts key usage to specific IAM roles. The compliance team discovers that some S3 objects are encrypted with AWS managed keys (SSE-S3) instead of the required SSE-KMS using the custom key. The security architect needs to ensure all future uploads use the customer-managed KMS key. After implementing a bucket policy that denies s3:PutObject if the required encryption is not present, the development team reports that their existing automation scripts fail with access denied errors. The scripts use the AWS SDK and do not explicitly set encryption headers. The security architect must find a solution that enforces encryption with the custom key while minimizing disruption. Which course of action BEST resolves the issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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
Modify the bucket policy to use a Deny effect with a condition on the s3:x-amz-server-side-encryption-aws-kms-key-id header being null, and also enable S3 default encryption with the custom KMS key so that objects uploaded without explicit headers are automatically encrypted with the correct key.
Option A is correct because it combines a bucket policy that denies s3:PutObject when the s3:x-amz-server-side-encryption-aws-kms-key-id header is null (ensuring the custom KMS key ID is explicitly provided) with S3 default encryption configured to use the same custom KMS key. This dual approach ensures that even if the SDK scripts do not set encryption headers, the default encryption will automatically apply the required KMS key, making the policy condition pass and avoiding access denied errors. The Deny condition on the null header forces explicit encryption headers when they are set, while default encryption handles the case where no headers are provided, thus enforcing compliance without breaking existing automation.
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.
- ✓
Modify the bucket policy to use a Deny effect with a condition on the s3:x-amz-server-side-encryption-aws-kms-key-id header being null, and also enable S3 default encryption with the custom KMS key so that objects uploaded without explicit headers are automatically encrypted with the correct key.
Why this is correct
Correct: Default encryption catches objects without headers, and the bucket policy denies explicit mismatches, enforcing both backward compatibility and compliance.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Implement AWS Config rules to detect non-compliant objects and automatically re-encrypt them with the correct key, while keeping the bucket policy unchanged.
Why it's wrong here
Incorrect: This is a corrective measure after the fact, not preventative; the bucket policy would still block scripts that omit headers.
- ✗
Remove the bucket policy and rely solely on S3 default encryption with the custom KMS key, because default encryption applies to all objects.
Why it's wrong here
Incorrect: Default encryption encrypts objects but does not prevent the development team from overriding the encryption with a non-compliant key if they explicitly set headers.
- ✗
Create a new S3 bucket with the required policy and migrate all data using AWS DataSync, then delete the old bucket.
Why it's wrong here
Incorrect: This adds complexity and migration time without addressing the immediate issue of failing uploads in the current bucket.
Common exam traps
Common exam trap: answer the scenario, not the keyword
ISC2 often tests the misconception that S3 default encryption alone is sufficient to enforce encryption compliance, but the trap here is that default encryption does not prevent explicit overrides, so a bucket policy with a Deny condition is still needed to block non-compliant uploads.
Detailed technical explanation
How to think about this question
Under the hood, S3 default encryption is applied at the bucket level and automatically encrypts objects that are uploaded without any encryption headers, but it does not prevent a PUT request that explicitly specifies a different encryption method (e.g., SSE-S3). The bucket policy condition s3:x-amz-server-side-encryption-aws-kms-key-id being null checks whether the request includes the specific KMS key ID header; if the header is absent (null), the Deny triggers, but if default encryption is enabled, S3 internally adds the required encryption headers before the policy evaluation, making the condition pass. This behavior is documented in AWS re:Post and is a common pattern for enforcing KMS encryption without breaking legacy clients.
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 developer is choosing between AES-256 (symmetric) and RSA-2048 (asymmetric) for encrypting a large file that will be sent to a partner. Symmetric encryption is fast but requires key exchange; asymmetric is slower but solves the key distribution problem. A hybrid approach — encrypt the file with AES, encrypt the AES key with RSA — is standard. Questions like this test whether you understand when each approach applies.
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 CCSP question test?
Cloud Data Security — This question tests Cloud Data Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Modify the bucket policy to use a Deny effect with a condition on the s3:x-amz-server-side-encryption-aws-kms-key-id header being null, and also enable S3 default encryption with the custom KMS key so that objects uploaded without explicit headers are automatically encrypted with the correct key. — Option A is correct because it combines a bucket policy that denies s3:PutObject when the s3:x-amz-server-side-encryption-aws-kms-key-id header is null (ensuring the custom KMS key ID is explicitly provided) with S3 default encryption configured to use the same custom KMS key. This dual approach ensures that even if the SDK scripts do not set encryption headers, the default encryption will automatically apply the required KMS key, making the policy condition pass and avoiding access denied errors. The Deny condition on the null header forces explicit encryption headers when they are set, while default encryption handles the case where no headers are provided, thus enforcing compliance without breaking existing automation.
What should I do if I get this CCSP 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: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
This CCSP practice question is part of Courseiva's free ISC2 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 CCSP exam.
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