ANS-C01 Network Security, Compliance and Governance Practice Question
A company is designing a multi-account architecture. They need to centralize VPC flow logs from all accounts into a single Amazon S3 bucket in the security account. The logs must be encrypted at rest using a customer-managed KMS key in the security account. Which combination of steps is required?
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
✓
Configure the KMS key policy to allow the log-producing accounts to use the key, and the S3 bucket policy to allow those accounts to write.
To centralize VPC flow logs with customer-managed KMS encryption, you need both a KMS key policy that grants the log-producing accounts permission to use the key (kms:Encrypt, kms:GenerateDataKey) and an S3 bucket policy that allows those accounts to write objects. Option A is wrong because SSE-S3 cannot be used with cross-account access in this context. Option B is wrong because using separate keys per account defeats centralization. Option D is wrong because without modifying the KMS key policy, cross-account encryption will fail.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Configure the S3 bucket policy to allow the log accounts to write; encryption is automatic with SSE-S3.
Why it's wrong here
Requires customer-managed KMS key, not SSE-S3.
- ✗
Create a KMS key in each account and configure the S3 bucket to use each key.
Why it's wrong here
Not centralized; each account uses its own key.
- ✓
Configure the KMS key policy to allow the log-producing accounts to use the key, and the S3 bucket policy to allow those accounts to write.
Why this is correct
Cross-account KMS requires key policy; bucket policy allows writes.
- ✗
Create a KMS key in the security account with no key policy changes; use bucket policies to allow cross-account writes.
Why it's wrong here
KMS key needs cross-account permissions in key policy.
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
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