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CAS-004 Practice Question: Is reviewing the configuration of an AWS S3…
A security engineer is reviewing the configuration of an AWS S3 bucket that stores customer data. Which of the following settings is most likely to cause a data breach?
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
✓
Bucket policy that allows public read access
A bucket policy allowing public read access exposes data to anyone. Option A (versioning) is a feature, not a risk. Option C (encryption) is secure. Option D (MFA delete) is a security control.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Versioning enabled on the bucket
Why it's wrong here
Versioning retains multiple object revisions, which supports recovery and does not expose data; it is a protective control. It tempts candidates because extra stored copies feel risky, and would be correct when the requirement is preserving prior object versions for rollback or compliance retention.
- ✓
Bucket policy that allows public read access
Why this is correct
A bucket policy granting public read access exposes every object to anonymous retrieval, so anyone with the URL can download customer data. This is the setting most likely to cause a breach, unlike encryption or versioning misconfigurations.
- ✗
Server-side encryption with AWS KMS
Why it's wrong here
Server-side encryption with AWS KMS protects data at rest, so it cannot itself cause a breach; the risk lies in public access settings or permissive bucket policies. It is tempting because KMS encryption is a genuine hardening control, and would be the right answer when the question asks how to meet encryption-at-rest compliance requirements.
- ✗
MFA delete enabled on the bucket
Why it's wrong here
MFA delete only guards object deletion and versioning changes; it does not expose data, so it cannot cause a breach. It is tempting because it is a genuine S3 security control, and it would be the right answer if the scenario asked how to protect against accidental or malicious deletion of critical objects.
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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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CAS-005 practice question is part of Courseiva's free CompTIA 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 CAS-005 exam.