The correct answer is to update the bucket policy to require the x-amz-server-side-encryption header set to 'aws:kms' and specify the desired KMS key ARN. This works because an S3 bucket policy can enforce SSE-KMS encryption by adding a condition that denies s3:PutObject unless the encryption header matches 'aws:kms' and the correct key ARN is used, ensuring all new uploads comply with the security policy without affecting existing objects. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of how bucket policy conditions override default encryption settings—a common trap is assuming default encryption alone enforces the requirement, but it only applies when no header is present, while a policy condition actively rejects non-compliant requests. Remember the memory tip: "Policy conditions police the headers; defaults only fill the gaps."
SCS-C02 Data Protection Practice Question
This SCS-C02 practice question tests your understanding of data protection. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 uses Amazon S3 to store sensitive documents. The security engineer notices that an S3 bucket named 'documents-prod' has been configured with a bucket policy that allows s3:PutObject from any principal, but only if the request includes the x-amz-server-side-encryption header set to 'AES256'. The company's security policy requires that all objects be encrypted at rest using server-side encryption with AWS KMS (SSE-KMS). The engineer needs to ensure that any new objects uploaded to the bucket are encrypted with SSE-KMS, and that existing objects remain accessible. What should the engineer do?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Update the bucket policy to require the x-amz-server-side-encryption header set to 'aws:kms' and specify the desired KMS key ARN
Option C is correct because adding a condition for KMS encryption to the bucket policy will enforce SSE-KMS for future uploads, and existing objects are still decryptable. Option A is wrong because changing default encryption does not enforce the policy. Option B is wrong because it ignores existing objects. Option D is wrong because it only affects future uploads via a specific encryption key, not the enforcement.
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.
✗
Create a new bucket with a bucket policy that requires SSE-KMS, and migrate all objects using S3 Batch Operations
Why it's wrong here
Migration is unnecessary; the existing bucket can be updated.
✗
Modify the bucket's default encryption configuration to use SSE-KMS
Why it's wrong here
Default encryption does not enforce encryption; it only applies if no header is provided.
✓
Update the bucket policy to require the x-amz-server-side-encryption header set to 'aws:kms' and specify the desired KMS key ARN
Why this is correct
This will enforce SSE-KMS for new uploads; existing objects are still valid.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable S3 Object Lock on the bucket to prevent overwrites, and use a lifecycle policy to expire objects that are not encrypted with SSE-KMS
Why it's wrong here
Object Lock does not enforce encryption.
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.
Data Protection — This question tests Data Protection — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Update the bucket policy to require the x-amz-server-side-encryption header set to 'aws:kms' and specify the desired KMS key ARN — Option C is correct because adding a condition for KMS encryption to the bucket policy will enforce SSE-KMS for future uploads, and existing objects are still decryptable. Option A is wrong because changing default encryption does not enforce the policy. Option B is wrong because it ignores existing objects. Option D is wrong because it only affects future uploads via a specific encryption key, not the enforcement.
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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