The correct action is to attach an S3 bucket policy that denies s3:PutObject unless the request includes the x-amz-server-side-encryption header set to aws:kms. This is necessary because the server access log shows a successful upload with encryption status “AES256,” which indicates SSE-S3 was used, not the required SSE-KMS. A bucket policy is the only way to enforce encryption at upload time by rejecting any PutObject call that lacks the KMS encryption header, whereas default encryption settings only apply to objects uploaded without any encryption header and do not block SSE-S3 requests. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of how to enforce encryption policies using S3 bucket policies versus default encryption or CloudTrail, with a common trap being to confuse a successful upload log with correct encryption. Remember the key distinction: default encryption is passive, but a bucket policy is active enforcement—think “policy to police, default to defer.”
DEA-C01 Data Security and Governance Practice Question
This DEA-C01 practice question tests your understanding of data security and governance. 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.
Refer to the exhibit. A data engineer reviews an Amazon S3 server access log entry for an object upload. The log shows a status of 200 and encryption status "AES256". The company policy requires that all data be encrypted with SSE-KMS. Which action should the engineer take to enforce this policy?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Attach an S3 bucket policy that denies s3:PutObject unless the request includes x-amz-server-side-encryption: aws:kms
Option C is correct because the log shows the object was encrypted with AES256 (SSE-S3), not KMS. The engineer should attach a bucket policy that denies PutObject unless the encryption header is aws:kms. Option A is wrong because the upload succeeded. Option B is wrong because CloudTrail does not prevent uploads. Option D is wrong because default encryption only applies to new objects without encryption headers, but the policy must deny SSE-S3.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Attach an S3 bucket policy that denies s3:PutObject unless the request includes x-amz-server-side-encryption: aws:kms
Why this is correct
Enforces SSE-KMS.
Related concept
Standard ACLs match source addresses.
✗
Revoke the IAM role's s3:PutObject permission
Why it's wrong here
The role is allowed; the issue is encryption type.
✗
Enable AWS CloudTrail data events to monitor future uploads
Why it's wrong here
Monitoring does not enforce policy.
✗
Enable S3 default encryption with SSE-KMS on the bucket
Why it's wrong here
Default encryption does not override explicit SSE-S3 headers.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DEA-C01 ACL questions on filtering logic and placement.
Data Security and Governance — This question tests Data Security and Governance — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Attach an S3 bucket policy that denies s3:PutObject unless the request includes x-amz-server-side-encryption: aws:kms — Option C is correct because the log shows the object was encrypted with AES256 (SSE-S3), not KMS. The engineer should attach a bucket policy that denies PutObject unless the encryption header is aws:kms. Option A is wrong because the upload succeeded. Option B is wrong because CloudTrail does not prevent uploads. Option D is wrong because default encryption only applies to new objects without encryption headers, but the policy must deny SSE-S3.
What should I do if I get this DEA-C01 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DEA-C01 ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A data engineer needs to restrict access to an Amazon S3 bucket so that only objects encrypted with a specific AWS KMS key can be uploaded. Which S3 bucket policy condition should be used?
Why A: The kms:EncryptionContext condition key is used to enforce encryption context, not the key itself. The s3:x-amz-server-side-encryption-aws-kms-key-id condition key is used to require a specific KMS key ID for server-side encryption. Option C is correct.
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This DEA-C01 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 DEA-C01 exam.
Question Discussion
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