The answer is to create an S3 bucket policy that denies PutObject if the x-amz-server-side-encryption header is not present. This approach works because bucket policies are evaluated before the upload completes, allowing you to reject any object that lacks the required encryption header, regardless of how the upload request is made. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding of how to enforce S3 object encryption using bucket policy as a preventive control, rather than relying on default encryption settings which can be overridden by explicit request headers. A common trap is assuming S3 default encryption covers all uploads, but it only applies when no encryption header is specified—a malicious or misconfigured client can still bypass it. For the exam, remember the memory tip: "Deny the headerless upload" to enforce encryption at the policy level, not the bucket level.
SOA-C02 Security and Compliance Practice Question
This SOA-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 company uses S3 to store sensitive data. To meet compliance requirements, all S3 buckets must be encrypted at rest. The security team notices that some objects in a bucket are not encrypted. What is the MOST efficient way to enforce encryption for all future objects?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create an S3 bucket policy that denies PutObject if the x-amz-server-side-encryption header is not present
Option D is correct because using a bucket policy to deny PutObject requests without the x-amz-server-side-encryption header ensures that any object uploaded without encryption is rejected. Option A is incorrect because S3 default encryption applies only to new objects, but objects can still be uploaded without encryption if the request explicitly specifies otherwise. Option B is incorrect because S3 inventory does not enforce encryption; it only reports. Option C is incorrect because manually re-uploading is not efficient and does not prevent future violations.
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 AWS Config managed rule to identify unencrypted objects and re-upload them manually
Why it's wrong here
Manual re-upload is inefficient and does not prevent future violations.
✗
Use S3 Inventory to list unencrypted objects and apply encryption via S3 Batch Operations
Why it's wrong here
Inventory reports but does not enforce; batch operations are reactive, not proactive.
✗
Enable default encryption on the bucket using AES-256
Why it's wrong here
Default encryption applies only to objects without encryption headers; objects can still be uploaded with no encryption.
✓
Create an S3 bucket policy that denies PutObject if the x-amz-server-side-encryption header is not present
Why this is correct
Bucket policy enforces encryption at upload time, rejecting unencrypted requests.
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.
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 SOA-C02 ACL questions on filtering logic and placement.
Security and Compliance — This question tests Security and Compliance — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Create an S3 bucket policy that denies PutObject if the x-amz-server-side-encryption header is not present — Option D is correct because using a bucket policy to deny PutObject requests without the x-amz-server-side-encryption header ensures that any object uploaded without encryption is rejected. Option A is incorrect because S3 default encryption applies only to new objects, but objects can still be uploaded without encryption if the request explicitly specifies otherwise. Option B is incorrect because S3 inventory does not enforce encryption; it only reports. Option C is incorrect because manually re-uploading is not efficient and does not prevent future violations.
What should I do if I get this SOA-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 SOA-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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