The answer is enabling default encryption on the S3 bucket using SSE-S3 and using a bucket policy to deny PutObject requests without encryption headers. Default encryption ensures that any object uploaded without explicit encryption settings is automatically encrypted at rest, while a bucket policy enforces encryption by rejecting unencrypted uploads at the API level. On the AWS Certified Data Engineer Associate DEA-C01 exam, this pairing tests your understanding that encryption enforcement requires both a preventive control (policy) and a default mechanism (bucket setting), often appearing as a two-answer question to distinguish from red herrings like CloudTrail or VPC endpoints. A common trap is assuming KMS alone enforces encryption, but KMS provides the key, not the policy rule. Remember the mnemonic: “Policy to deny, default to apply” — the bucket policy denies unencrypted writes, and default encryption applies SSE-S3 to any object that slips through without headers.
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.
A data engineer needs to enforce that all data in an Amazon S3 bucket is encrypted at rest. Which of the following can be used to achieve this? (Choose TWO.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure a bucket policy to deny PutObject if encryption headers are missing
Option B and D are correct. S3 bucket policies can deny PutObject requests without encryption headers, and SSE-S3 ensures encryption at rest. Option A is wrong because CloudTrail logs API calls but does not enforce encryption. Option C is wrong because VPC endpoints provide network isolation, not encryption. Option E is wrong because KMS alone does not enforce encryption on 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.
✗
Use AWS CloudTrail to monitor for unencrypted objects
Why it's wrong here
CloudTrail monitors but does not enforce.
✗
Use VPC endpoints to restrict access
Why it's wrong here
VPC endpoints do not enforce encryption.
✓
Configure a bucket policy to deny PutObject if encryption headers are missing
Why this is correct
This policy enforces encryption on uploads.
Related concept
Standard ACLs match source addresses.
✓
Enable default encryption on the S3 bucket using SSE-S3
Why this is correct
Default encryption ensures all new objects are encrypted.
Related concept
Standard ACLs match source addresses.
✗
Use AWS KMS to generate encryption keys for the bucket
Why it's wrong here
KMS alone does not enforce encryption.
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: Configure a bucket policy to deny PutObject if encryption headers are missing — Option B and D are correct. S3 bucket policies can deny PutObject requests without encryption headers, and SSE-S3 ensures encryption at rest. Option A is wrong because CloudTrail logs API calls but does not enforce encryption. Option C is wrong because VPC endpoints provide network isolation, not encryption. Option E is wrong because KMS alone does not enforce encryption on 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.
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Question Discussion
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