This SCS-C02 practice question tests your understanding of data protection. 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 company uses S3 to store sensitive customer data. The security team requires that all objects uploaded to S3 be encrypted at rest using server-side encryption with AWS KMS managed keys (SSE-KMS). A developer reports that some objects are being stored unencrypted. What is the MOST effective way to enforce this requirement?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a bucket policy to deny s3:PutObject if encryption is not set to aws:kms
Option D is correct because an S3 bucket policy with a Deny condition for s3:PutObject without the x-amz-server-side-encryption header set to aws:kms will block unencrypted uploads. Option A is wrong because SSE-C uses customer-provided keys, not KMS. Option B is wrong because bucket policies are more direct than service control policies for this. Option C is wrong because default encryption only applies when no encryption is specified, but a PUT request can still override it.
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.
✗
Enable default encryption on the bucket using SSE-S3
Why it's wrong here
SSE-S3 does not use KMS keys.
✓
Use a bucket policy to deny s3:PutObject if encryption is not set to aws:kms
Why this is correct
Policy condition can enforce SSE-KMS.
Related concept
Standard ACLs match source addresses.
✗
Use an SCP to deny s3:PutObject without encryption
Why it's wrong here
SCPs are not effective at resource level.
✗
Set a bucket policy to require the x-amz-server-side-encryption header
Why it's wrong here
Default encryption does not enforce encryption header.
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 SCS-C02 ACL questions on filtering logic and placement.
Data Protection — This question tests Data Protection — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Use a bucket policy to deny s3:PutObject if encryption is not set to aws:kms — Option D is correct because an S3 bucket policy with a Deny condition for s3:PutObject without the x-amz-server-side-encryption header set to aws:kms will block unencrypted uploads. Option A is wrong because SSE-C uses customer-provided keys, not KMS. Option B is wrong because bucket policies are more direct than service control policies for this. Option C is wrong because default encryption only applies when no encryption is specified, but a PUT request can still override it.
What should I do if I get this SCS-C02 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 SCS-C02 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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