DEA-C01 S3 bucket policy Practice Question
A data engineer notices that an Amazon S3 bucket policy is overly permissive. What is the best practice to restrict access while maintaining required permissions?
⚠ Common exam trap
Do not confuse IAM policies with bucket policies. Attaching an IAM policy to a user does not override an overly permissive bucket policy; both must be considered together.
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
✓
Write a new bucket policy that denies all actions.
The bucket policy is overly permissive, so writing a new bucket policy that denies all actions immediately restricts all access. While this may temporarily block required permissions, it is the most direct way to address the bucket policy issue; you can then refine the policy to allow only necessary actions. Option D does not change the bucket policy and thus does not resolve the problem. Option A makes permissions even more permissive. Option C is not a standard AWS feature.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Grant full S3 access using a new IAM policy.
Why it's wrong here
Granting full S3 access via a new IAM policy makes permissions even more permissive, which is the opposite of the required restriction. It does not modify the bucket policy.
- ✓
Write a new bucket policy that denies all actions.
Why this is correct
Writing a new bucket policy that denies all actions directly restricts the overly permissive bucket policy. While this may be too restrictive initially, it is the only option that modifies the bucket policy to immediately stop the over-permissive access. You can then add specific allows to maintain required permissions.
- ✗
Use an S3 blocklist to restrict access.
Why it's wrong here
There is no such feature as an S3 blocklist in AWS. This is not a valid method to restrict access.
- ✗
Attach the AWS managed policy AmazonS3ReadOnlyAccess to the IAM user.
Why it's wrong here
Attaching the AmazonS3ReadOnlyAccess managed policy to the IAM user does not change the bucket policy. If the bucket policy still grants full access, the user will still have full access despite having a read-only IAM policy. Therefore, this option does not restrict the overly permissive bucket policy.
Visual reference
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 |
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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