Centrally Enforce S3 Block Public Access Across All AWS Accounts Using SCP
A company has multiple AWS accounts managed via AWS Organizations. The security team requires that all S3 buckets across all accounts must block public access. How can this be enforced centrally with minimal operational overhead?
Quick Answer
The answer is to create a service control policy (SCP) that denies the s3:PutBucketPublicAccessBlock action unless the request includes the required public access block settings. This is correct because SCPs applied at the AWS Organizations root or organizational unit level provide a preventive guardrail that enforces S3 block public access across all accounts before any action can occur, eliminating the need for per-account configuration and minimizing operational overhead. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding of centralized governance versus detective controls—a common trap is choosing AWS Config rules or Lambda remediation, which are reactive and add overhead, whereas SCPs enforce the policy proactively. Remember that SCPs cannot grant permissions, only deny or allowlist actions, so you must pair the deny with a condition key like s3:PutBucketPublicAccessBlock to require the specific settings. Memory tip: think “SCP stops the put” to recall that the SCP blocks the API call that would disable public access blocks.
⚠ Common exam trap
Many candidates choose AWS Config (option A) because it is a common detective control, but they overlook that SCPs are the only preventive control that works centrally across all accounts with zero per-account setup.
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 service control policy (SCP) to deny s3:PutBucketPublicAccessBlock actions with conditions that require public access block settings.
An SCP applied at the AWS Organizations root or OU level can centrally deny the `s3:PutBucketPublicAccessBlock` action unless the request includes specific public access block settings. This enforces the security requirement across all accounts without per-account configuration, minimizing operational overhead. SCPs are the only mechanism that can prevent actions at the account level before they occur, making them ideal for mandatory security baselines.
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 AWS Config in each account and create a rule to mark public buckets as non-compliant.
Why it's wrong here
AWS Config only detects non-compliance; it does not enforce or prevent actions.
- ✗
Create an IAM role in each account with a policy that denies public access modifications and assign it to all users.
Why it's wrong here
IAM roles are per-account and require manual setup; they cannot enforce restrictions on all principals.
- ✗
Use a bucket policy on each existing bucket to deny public access and rely on AWS Config to detect new buckets.
Why it's wrong here
Bucket policies are per-bucket and do not prevent creation of new public buckets.
- ✓
Create a service control policy (SCP) to deny s3:PutBucketPublicAccessBlock actions with conditions that require public access block settings.
Why this is correct
SCPs can centrally enforce restrictions across all accounts in the organization.
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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Same concept, more angles
1 more way this is tested on SAP-C02
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company has multiple AWS accounts managed via AWS Organizations. The security team requires that all S3 buckets across all accounts be encrypted with AWS KMS and that bucket policies enforce HTTPS. What is the MOST efficient way to enforce these policies across all accounts?
medium- A.Apply a service control policy (SCP) to the management account.
- B.Create a custom AWS Lambda function to monitor and remediate non-compliant buckets.
- ✓ C.Apply a service control policy (SCP) to the organizational unit (OU) containing all accounts.
- D.Use AWS Config rules with automatic remediation in each account.
Why C: Applying an SCP at the OU level that denies S3 bucket creation/updates without KMS encryption and HTTPS enforcement provides centralized enforcement across all accounts in the OU. This is the most efficient method as it prevents non-compliant actions at the API level. Option A is incorrect because SCPs applied to the management account do not affect member accounts and the management account itself is not restricted by SCPs. Option B is incorrect because while Lambda functions could remediate, they are reactive and require per-account deployment, making them less efficient than proactive SCP enforcement. Option D is incorrect because AWS Config rules can detect non-compliance but do not automatically enforce; automatic remediation may require additional setup and is also reactive.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SAP-C02 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 SAP-C02 exam.