The correct answer is to add a Deny statement for s3:PutObject with a condition key of s3:x-amz-server-side-encryption set to aws:kms. This works because the condition explicitly checks the request header for the encryption type, and if it is not present or not set to aws:kms, the policy denies the upload. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of S3 bucket policies as a preventive control for data-at-rest encryption, often appearing as a multi-option question where traps include requiring a specific KMS key ID or mixing in SecureTransport conditions. A common mistake is selecting a policy that demands a particular key ARN, which would block valid uploads using any other KMS key. Remember the core rule: to enforce SSE-KMS without locking to a single key, deny unless the encryption header equals aws:kms—think of it as “deny the method, not the key.”
SCS-C02 Data Protection Practice Question
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 stores sensitive customer data in Amazon S3. They want to ensure that all objects are encrypted at rest using server-side encryption with AWS KMS. Which S3 bucket policy statement should be added to deny uploads that do not request SSE-KMS?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Deny PutObject unless 's3:x-amz-server-side-encryption' is 'aws:kms'
Option A is correct because the condition 's3:x-amz-server-side-encryption' with 'aws:SecureTransport' is not the right condition. Option B uses 's3:x-amz-server-side-encryption-aws-kms-key-id' which is too specific. Option C is the correct standard policy to deny PutObject without SSE-KMS. Option D is wrong because it requires a specific KMS key ID, not just any KMS key.
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.
✗
Deny PutObject unless 's3:x-amz-server-side-encryption' is 'AES256'
Why it's wrong here
This requires SSE-S3, not SSE-KMS.
✓
Deny PutObject unless 's3:x-amz-server-side-encryption' is 'aws:kms'
Why this is correct
This condition ensures the object is encrypted with SSE-KMS.
Related concept
Standard ACLs match source addresses.
✗
Deny PutObject unless 'aws:SourceArn' equals the bucket ARN
Why it's wrong here
This condition is about source ARN, not encryption.
✗
Deny PutObject unless 's3:x-amz-server-side-encryption-aws-kms-key-id' is present
Why it's wrong here
This condition requires a specific key ID, but the question does not specify a particular key.
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: Deny PutObject unless 's3:x-amz-server-side-encryption' is 'aws:kms' — Option A is correct because the condition 's3:x-amz-server-side-encryption' with 'aws:SecureTransport' is not the right condition. Option B uses 's3:x-amz-server-side-encryption-aws-kms-key-id' which is too specific. Option C is the correct standard policy to deny PutObject without SSE-KMS. Option D is wrong because it requires a specific KMS key ID, not just any KMS key.
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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