This SCS-C02 practice question tests your understanding of infrastructure security. 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 wants to restrict access to an S3 bucket so that only objects uploaded with server-side encryption using AWS KMS are allowed. The bucket policy uses the 's3:x-amz-server-side-encryption' condition key. However, users can still upload unencrypted objects. What is the most likely reason?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
The user's IAM policy overrides the bucket policy.
Why wrong: Bucket policies are evaluated before user policies; a Deny in the bucket policy would override any Allow.
B
The bucket policy uses an Allow effect instead of Deny for the condition.
The condition must be used in a Deny statement to block unencrypted uploads. An Allow statement only permits encrypted uploads but does not prevent unencrypted ones.
C
The condition key is misspelled.
Why wrong: The condition key 's3:x-amz-server-side-encryption' is correctly spelled.
D
The bucket policy does not explicitly deny s3:PutObject.
Why wrong: A Deny statement with the condition is sufficient; explicit Deny on the action is not needed.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The bucket policy uses an Allow effect instead of Deny for the condition.
Option C is correct because the condition key 's3:x-amz-server-side-encryption' must be combined with a Deny effect to block unencrypted uploads. Option A is wrong because the condition key is set to 'aws:kms', which is correct. Option B is wrong because the bucket policy does not need to explicitly deny the s3:PutObject action; a Deny with the condition works. Option D is wrong because the bucket policy is evaluated before the user policy.
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.
✗
The user's IAM policy overrides the bucket policy.
Why it's wrong here
Bucket policies are evaluated before user policies; a Deny in the bucket policy would override any Allow.
✓
The bucket policy uses an Allow effect instead of Deny for the condition.
Why this is correct
The condition must be used in a Deny statement to block unencrypted uploads. An Allow statement only permits encrypted uploads but does not prevent unencrypted ones.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
✗
The condition key is misspelled.
Why it's wrong here
The condition key 's3:x-amz-server-side-encryption' is correctly spelled.
✗
The bucket policy does not explicitly deny s3:PutObject.
Why it's wrong here
A Deny statement with the condition is sufficient; explicit Deny on the action is not needed.
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.
Infrastructure Security — This question tests Infrastructure Security — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: The bucket policy uses an Allow effect instead of Deny for the condition. — Option C is correct because the condition key 's3:x-amz-server-side-encryption' must be combined with a Deny effect to block unencrypted uploads. Option A is wrong because the condition key is set to 'aws:kms', which is correct. Option B is wrong because the bucket policy does not need to explicitly deny the s3:PutObject action; a Deny with the condition works. Option D is wrong because the bucket policy is evaluated before the user policy.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Standard ACLs match source addresses.
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