SOA-C02 Security and Compliance Practice Question
A SysOps administrator is asked to ensure that all objects in an S3 bucket are encrypted at rest using a customer-managed KMS key. The bucket currently has default encryption set to SSE-S3. What must be done to meet the requirement?
⚠ Common exam trap
A common mix-up: candidates assume changing the bucket's default encryption automatically re-encrypts all existing objects, but AWS S3 default encryption only applies to new uploads, not to objects already in the bucket.
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
✓
Update the bucket's default encryption to SSE-KMS using the customer-managed key, and re-upload existing objects.
Default encryption on an S3 bucket only applies to newly uploaded objects; existing objects remain encrypted with the previous method (SSE-S3). To ensure all objects are encrypted at rest with a customer-managed KMS key, you must update the bucket's default encryption to SSE-KMS with the desired key and then re-upload (or copy) existing objects so they inherit the new encryption setting. Simply changing the default encryption does not retroactively re-encrypt objects already stored.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Update the bucket's default encryption to SSE-KMS using the customer-managed key, and re-upload existing objects.
Why this is correct
Default encryption is applied only when an object is first written to Amazon S3; changing the bucket's default from SSE-S3 or none to SSE-KMS with a customer-managed key does not retroactively alter objects that are already stored. To satisfy the requirement, the administrator must update the default encryption configuration and then copy each existing object back over itself (or re-upload it) using an operation that explicitly applies SSE-KMS, because the bucket's default will not touch the old objects. Only this combination ensures both current and future objects meet the SSE-KMS policy.
- ✗
Add a bucket policy that denies s3:PutObject without the x-amz-server-side-encryption header.
Why it's wrong here
Adding a bucket policy that denies s3:PutObject when the x-amz-server-side-encryption header is absent or not equal to aws:kms will enforce SSE-KMS for new writes, but it does nothing to change the bucket's default encryption configuration and leaves already-stored objects unencrypted with the customer-managed key. Moreover, this policy can be circumvented by requests that omit the header if the bucket already has a default encryption rule, and it requires clients to explicitly send headers rather than relying on server-side defaults. The task specifically asks to ensure all objects are encrypted, not just future PUTs, so this action is incomplete.
- ✗
Apply a service control policy to enforce SSE-KMS across the organization.
Why it's wrong here
A service control policy (SCP) operates at the AWS Organizations level and can only restrict the IAM permissions that member accounts' principals can use; it cannot directly modify an S3 bucket's default encryption settings or rewrite object data. While an SCP could deny s3:PutObject to enforce encryption headers, it still does not change the existing bucket configuration and cannot retroactively encrypt existing objects. Therefore, applying an SCP is not the correct mechanism to satisfy the requirement of ensuring all objects in the bucket are encrypted.
- ✗
Enable S3 Versioning and set the bucket's default encryption to SSE-KMS.
Why it's wrong here
Enabling S3 Versioning is unrelated to encryption—it creates new object versions on writes but does not alter the encryption attributes of existing objects or existing versions. Even when versioning is enabled and the bucket default encryption is then set to SSE-KMS, the pre-existing object versions remain encrypted with their original settings; only newly uploaded objects/versions receive the new default. To meet the requirement, the administrator must re-upload/copy the existing objects, which the option does not include, making it an incorrect answer.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
Go deeper
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SOA-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 SOA-C02 exam.