- A
Use an S3 bucket policy that requires the x-amz-server-side-encryption-aws-kms-key-id header to match a specific KMS key.
Why wrong: While more restrictive, this does not enforce the use of SSE-KMS; an object could be encrypted with SSE-S3 and still include a KMS key ID header, causing confusion.
- B
Use an S3 bucket policy with a condition that requires the x-amz-server-side-encryption header to be present.
Why wrong: This condition alone does not enforce a specific encryption method; it only requires the header to be present.
- C
Configure the bucket's default encryption to use SSE-KMS.
Why wrong: Default encryption only applies when no encryption header is provided; it does not deny uploads with other encryption or without encryption.
- D
Use an S3 bucket policy with a condition that denies PutObject if the x-amz-server-side-encryption header is not set to 'aws:kms'.
This policy denies uploads that do not use SSE-KMS, effectively enforcing the requirement.
Quick Answer
The correct answer is to use an S3 bucket policy with a condition that denies PutObject if the x-amz-server-side-encryption header is not set to 'aws:kms'. This works because S3 bucket policies can evaluate request headers at upload time, allowing you to enforce SSE-KMS by rejecting any PUT request that lacks the required encryption header. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding that bucket policies enforce compliance on incoming requests, whereas default encryption settings only apply when no encryption header is provided—they do not prevent unencrypted uploads. A common trap is confusing default encryption with policy enforcement; remember that default encryption is a fallback, not a gate. For the exam, think of the bucket policy as a bouncer checking IDs (the encryption header) at the door, while default encryption is just a backup coat check. Memory tip: “Deny without KMS header” ensures every object is KMS-encrypted from the start.
SCS-C02 Identity and Access Management Practice Question
This SCS-C02 practice question tests your understanding of identity and access management. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 has an S3 bucket that contains sensitive data. The security team wants to ensure that all objects uploaded to the bucket are encrypted at rest using server-side encryption with AWS KMS (SSE-KMS). What should the security team do to enforce this requirement?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Use an S3 bucket policy with a condition that denies PutObject if the x-amz-server-side-encryption header is not set to 'aws:kms'.
Option C is correct because an S3 bucket policy denying PutObject requests that do not include the x-amz-server-side-encryption header set to aws:kms ensures that only objects encrypted with SSE-KMS can be uploaded. Option A is wrong because bucket policies cannot enforce default encryption; they can only deny requests based on conditions. Option B is wrong because enabling default encryption does not prevent uploads without encryption headers. Option D is wrong because SSE-S3 is not KMS encryption.
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 an S3 bucket policy that requires the x-amz-server-side-encryption-aws-kms-key-id header to match a specific KMS key.
Why it's wrong here
While more restrictive, this does not enforce the use of SSE-KMS; an object could be encrypted with SSE-S3 and still include a KMS key ID header, causing confusion.
- ✗
Use an S3 bucket policy with a condition that requires the x-amz-server-side-encryption header to be present.
Why it's wrong here
This condition alone does not enforce a specific encryption method; it only requires the header to be present.
- ✗
Configure the bucket's default encryption to use SSE-KMS.
Why it's wrong here
Default encryption only applies when no encryption header is provided; it does not deny uploads with other encryption or without encryption.
- ✓
Use an S3 bucket policy with a condition that denies PutObject if the x-amz-server-side-encryption header is not set to 'aws:kms'.
Why this is correct
This policy denies uploads that do not use SSE-KMS, effectively enforcing the requirement.
Related concept
Standard ACLs match source addresses.
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.
Trap categories for this question
Similar concept trap
While more restrictive, this does not enforce the use of SSE-KMS; an object could be encrypted with SSE-S3 and still include a KMS key ID header, causing confusion.
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.
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Identity and Access Management — study guide chapter
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Identity and Access Management practice questions
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FAQ
Questions learners often ask
What does this SCS-C02 question test?
Identity and Access Management — This question tests Identity and Access Management — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Use an S3 bucket policy with a condition that denies PutObject if the x-amz-server-side-encryption header is not set to 'aws:kms'. — Option C is correct because an S3 bucket policy denying PutObject requests that do not include the x-amz-server-side-encryption header set to aws:kms ensures that only objects encrypted with SSE-KMS can be uploaded. Option A is wrong because bucket policies cannot enforce default encryption; they can only deny requests based on conditions. Option B is wrong because enabling default encryption does not prevent uploads without encryption headers. Option D is wrong because SSE-S3 is not KMS encryption.
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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Last reviewed: Jun 20, 2026
This SCS-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SCS-C02 exam.
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