ISC Infrastructure And System Security Practice Question
You are configuring AWS S3 bucket security for sensitive data. Which THREE of the following are best practices to prevent unauthorized public access?
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
✓
Apply a bucket policy with an explicit Deny for s3:PutObject for unauthenticated users
Block Public Access settings at the account level, using Bucket Policies with Deny statements, and enforcing S3 Block Public Access at the bucket level are the primary defense-in-depth measures.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Apply a bucket policy with an explicit Deny for s3:PutObject for unauthenticated users
Why this is correct
Explicit Deny statements always override Allow statements.
- ✓
Enable S3 Block Public Access at the bucket level
Why this is correct
This ensures the specific bucket cannot be made public regardless of other settings.
- ✗
Enable Server-Side Encryption with KMS
Why it's wrong here
Encryption protects data at rest but does not prevent public access.
- ✓
Enable S3 Block Public Access at the account level
Why this is correct
This acts as a global override preventing accidental public bucket creation.
- ✗
Use IAM users for all S3 interactions
Why it's wrong here
Using IAM users is a best practice for identity, but does not inherently block public access configurations.
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 |
About these practice questions
One of 208 original ISC practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed August 2026 · checked against the official (ISC)² exam blueprint
This ISC practice question is part of Courseiva's free (ISC)² 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 ISC exam.