DEA-C01 Data Security and Governance Practice Question
A data engineer notices that an S3 bucket policy allows access to a user from another AWS account, but the access is being denied. What could be the reason?
⚠ Common exam trap
Watch out — candidates often assume a bucket policy alone is sufficient for cross-account access, forgetting that the requesting account's IAM user must also have explicit permissions, which is a classic AWS cross-account authorization nuance.
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
✓
The other account's IAM user does not have permissions to access the bucket
For cross-account S3 access to succeed, both the bucket policy (resource-based policy) and the IAM user policy (identity-based policy) in the other account must grant the necessary permissions. Option B is correct because even if the bucket policy allows access from the other account, the IAM user in that account must have an explicit IAM policy that permits the S3 action (e.g., s3:GetObject) on the bucket. Without this, the request is denied by the other account's own IAM evaluation.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The bucket policy does not include KMS permissions
Why it's wrong here
KMS permissions govern encrypted object access, not the cross-account authorisation decision itself; a bucket policy granting access still fails if the trusting account's IAM identity lacks permission. It is tempting because KMS key policies commonly cause AccessDenied on encrypted objects, which would be the answer if SSE-KMS were in play.
- ✓
The other account's IAM user does not have permissions to access the bucket
Why this is correct
Cross-account S3 access requires both the bucket policy to allow the principal and the principal's own IAM identity policy to permit the S3 action. The bucket policy alone is insufficient, so the missing identity-based permission causes the denial.
- ✗
S3 does not support cross-account access
Why it's wrong here
S3 explicitly supports cross-account access through bucket policies and IAM roles, so this claim is false. It is tempting because cross-account setups do require both accounts to grant permission, but that dual-consent requirement is the actual mechanism, not a blanket lack of support.
- ✗
The bucket is in a different region
Why it's wrong here
S3 bucket names are globally unique and access policies are region-agnostic; a bucket in another region does not deny a permitted cross-account principal. It is tempting because latency and data-residency concerns accompany cross-region access, but region placement never overrides an explicit bucket policy allow.
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 DEA-C01 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 DEA-C01 exam.