ANS-C01 Network Management and Operations Practice Question
A company wants to centralize logging of VPC Flow Logs from multiple accounts into a single Amazon S3 bucket. The logs must be encrypted at rest using an AWS KMS CMK. What is the recommended approach?
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
✓
Create a centralized S3 bucket with default encryption using a KMS CMK and a bucket policy that allows cross-account writes from the source accounts.
The recommended approach uses a centralized S3 bucket with default encryption using a KMS CMK and a bucket policy that allows cross-account writes. This ensures logs are encrypted at rest centrally without requiring per-account KMS keys. Option A is wrong because KMS keys in each account would complicate key management and cross-account access. Option C is wrong because SSE-S3 encryption does not use a CMK and does not provide the same level of control. Option D is wrong because denying access unless encryption headers are present is not a reliable way to enforce encryption; bucket policies can be bypassed if headers are not included, and shared KMS keys are not recommended.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enable encryption on VPC Flow Logs using a KMS key in each account and aggregate logs using AWS Logs cross-account subscription.
Why it's wrong here
Cross-account subscription is complex and not directly to S3.
- ✓
Create a centralized S3 bucket with default encryption using a KMS CMK and a bucket policy that allows cross-account writes from the source accounts.
Why this is correct
This ensures encryption and centralized logging.
- ✗
Create a bucket with SSE-S3 encryption and have each account write flow logs directly.
Why it's wrong here
SSE-S3 uses Amazon S3-managed keys, not a CMK.
- ✗
Use a single bucket with a bucket policy that denies access unless encryption headers are present, and use a KMS key shared across accounts.
Why it's wrong here
This does not ensure encryption at rest, only enforces headers.
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 ANS-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 ANS-C01 exam.