The correct answer is that the first Deny statement only blocks encryption types other than `aws:kms`, inadvertently allowing SSE-S3 with `AES256` to pass through. This happens because the policy condition `StringNotEquals s3:x-amz-server-side-encryption aws:kms` only triggers a Deny when the encryption header is not exactly `aws:kms`; since SSE-S3 uses the value `AES256`, it does not match `aws:kms`, so the Deny never fires, and unencrypted or SSE-S3 uploads succeed. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this tests your ability to read bucket policy conditions precisely—a common trap is assuming a Deny for “not KMS” catches all non-KMS encryption, but it actually only catches values that are not `aws:kms`, leaving `AES256` untouched. Memory tip: think of the condition as a bouncer who only checks for a specific VIP pass (`aws:kms`); anyone holding a different valid pass (`AES256`) walks right in.
DOP-C02 Security and Compliance Practice Question
This DOP-C02 practice question tests your understanding of security and compliance. 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 DevOps engineer applies the S3 bucket policy shown in the exhibit to enforce encryption and secure transport. After applying the policy, users report that they can still upload objects without encryption. What is the most likely cause?
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The first Deny statement only denies encryption types other than aws:kms, but allows encryption with AES256.
Option C is correct because the first Deny statement in the bucket policy uses a condition that checks if the `s3:x-amz-server-side-encryption` header is not equal to `aws:kms`. This means it only denies uploads that use encryption types other than `aws:kms`, such as `AES256` (SSE-S3) or no encryption. Since `AES256` is not `aws:kms`, the Deny does not trigger for SSE-S3 uploads, allowing them to proceed without the required KMS encryption.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 Null condition incorrectly allows uploads without encryption.
Why it's wrong here
Null condition denies when encryption header is missing, but if AES256 is provided, the header is not null.
✗
The bucket policy does not apply to cross-account uploads.
Why it's wrong here
The policy applies to all principals, including cross-account.
✓
The first Deny statement only denies encryption types other than aws:kms, but allows encryption with AES256.
Why this is correct
The condition StringNotEquals aws:kms does not deny AES256 because AES256 is not equal to aws:kms, so the Deny does not apply.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The bucket policy lacks an explicit Allow statement for s3:PutObject.
Why it's wrong here
Deny statements are effective without an explicit Allow.
Common exam traps
Common exam trap: answer the scenario, not the keyword
AWS often tests the nuance that a `StringNotEquals` condition in a Deny statement only blocks the specified value, not all other values, leading candidates to mistakenly think the Deny covers all encryption types when it only covers the one explicitly listed.
Detailed technical explanation
How to think about this question
The condition `StringNotEquals` in the first Deny statement evaluates the `s3:x-amz-server-side-encryption` header value. When a client uploads with `x-amz-server-side-encryption: AES256`, the condition `StringNotEquals` returns true (since `AES256` is not `aws:kms`), but the Deny effect only applies if the condition is true; however, the Deny is intended to block non-KMS encryption, but it incorrectly allows `AES256` because the condition does not match `aws:kms`. In real-world scenarios, this misconfiguration could lead to compliance violations where data is encrypted with SSE-S3 instead of the required KMS key, potentially bypassing key rotation or audit controls.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Security and Compliance — This question tests Security and Compliance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The first Deny statement only denies encryption types other than aws:kms, but allows encryption with AES256. — Option C is correct because the first Deny statement in the bucket policy uses a condition that checks if the `s3:x-amz-server-side-encryption` header is not equal to `aws:kms`. This means it only denies uploads that use encryption types other than `aws:kms`, such as `AES256` (SSE-S3) or no encryption. Since `AES256` is not `aws:kms`, the Deny does not trigger for SSE-S3 uploads, allowing them to proceed without the required KMS encryption.
What should I do if I get this DOP-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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?
Read the scenario before looking for a memorised answer.
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