- A
Use the AWS CLI to copy the objects to themselves with the --sse-kms-key-id parameter.
Why wrong: Copying objects to themselves with the AWS CLI and --sse-kms-key-id parameter does not re-encrypt in place; it would require a full copy to a new location and back, which is inefficient.
- B
Modify the bucket policy to deny access to objects not encrypted with the KMS key.
Why wrong: Modifying the bucket policy to deny access to unencrypted objects only prevents access to those objects, but does not encrypt them; it would also disrupt ongoing access.
- C
Delete the unencrypted objects and re-upload them with encryption.
Why wrong: Deleting and re-uploading objects is disruptive and inefficient; it can cause data loss and access interruptions.
- D
Use S3 Batch Operations with a Lambda function to apply SSE-KMS encryption to all existing objects using the KMS key.
S3 Batch Operations with a Lambda function can re-encrypt all existing objects using SSE-KMS with the required KMS key, without disrupting data access.
DEA-C01 Data Security and Governance Practice Question
This DEA-C01 practice question tests your understanding of data security and governance. 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 Amazon S3 to store sensitive customer data. The security policy requires that all objects in the bucket be encrypted at rest using server-side encryption with a customer-managed KMS key. The data engineer has enabled default encryption on the bucket using SSE-KMS with the required KMS key. However, a security scan reveals that some objects in the bucket are not encrypted with the KMS key. The objects were uploaded before the default encryption was enabled. The data engineer needs to ensure that all objects are encrypted with the KMS key without disrupting ongoing data access. What should the data engineer do?
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 S3 Batch Operations with a Lambda function to apply SSE-KMS encryption to all existing objects using the KMS key.
Option D is correct because S3 Batch Operations can apply SSE-KMS encryption to existing objects without disrupting access. It uses a Lambda function to re-encrypt each object with the specified KMS key. Option A is wrong because copying objects to themselves with the --sse-kms-key-id parameter does not work - it requires a full copy to a new location and back. Option B is wrong because the bucket policy only prevents new unencrypted uploads, it does not fix existing objects. Option C is wrong because deleting and re-uploading disrupts access and is inefficient.
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 the AWS CLI to copy the objects to themselves with the --sse-kms-key-id parameter.
Why it's wrong here
Copying objects to themselves with the AWS CLI and --sse-kms-key-id parameter does not re-encrypt in place; it would require a full copy to a new location and back, which is inefficient.
- ✗
Modify the bucket policy to deny access to objects not encrypted with the KMS key.
Why it's wrong here
Modifying the bucket policy to deny access to unencrypted objects only prevents access to those objects, but does not encrypt them; it would also disrupt ongoing access.
- ✗
Delete the unencrypted objects and re-upload them with encryption.
Why it's wrong here
Deleting and re-uploading objects is disruptive and inefficient; it can cause data loss and access interruptions.
- ✓
Use S3 Batch Operations with a Lambda function to apply SSE-KMS encryption to all existing objects using the KMS key.
Why this is correct
S3 Batch Operations with a Lambda function can re-encrypt all existing objects using SSE-KMS with the required KMS key, without disrupting data access.
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.
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 |
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 DEA-C01 ACL questions on filtering logic and placement.
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FAQ
Questions learners often ask
What does this DEA-C01 question test?
Data Security and Governance — This question tests Data Security and Governance — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Use S3 Batch Operations with a Lambda function to apply SSE-KMS encryption to all existing objects using the KMS key. — Option D is correct because S3 Batch Operations can apply SSE-KMS encryption to existing objects without disrupting access. It uses a Lambda function to re-encrypt each object with the specified KMS key. Option A is wrong because copying objects to themselves with the --sse-kms-key-id parameter does not work - it requires a full copy to a new location and back. Option B is wrong because the bucket policy only prevents new unencrypted uploads, it does not fix existing objects. Option C is wrong because deleting and re-uploading disrupts access and is inefficient.
What should I do if I get this DEA-C01 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 DEA-C01 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
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