- A
AWS Config with the s3-bucket-public-read-prohibited managed rule
Why wrong: AWS Config is a detective service that evaluates resource configurations against rules. The s3-bucket-public-read-prohibited rule can detect buckets that allow public read access, but it does not prevent the bucket from being created or configured with public access. The scenario explicitly requires a preventive control, not a detective one.
- B
Amazon S3 Block Public Access at the account level
Amazon S3 Block Public Access provides centralized controls that can be applied at the account level. When enabled, these settings override any bucket-level policies that grant public access, preventing both new and existing buckets from ever being made publicly accessible. This is the preventive control described in the scenario.
- C
AWS Identity and Access Management (IAM) policy with a condition that denies s3:PutBucketPolicy for any action that grants public access
Why wrong: While an IAM policy with a condition key like s3:PutBucketPublicAccessBlock or a specific condition can deny PutBucketPolicy for public grants, it only applies to IAM users and roles that have the policy attached. It does not prevent the account root user or other authorized principals from making buckets public. It also does not apply to existing buckets that were made public before the policy was created. Therefore, it is not a comprehensive preventive control across the entire account.
- D
Amazon GuardDuty with a finding suppression rule for S3 public access events
Why wrong: Amazon GuardDuty is a threat detection service that monitors for malicious activity and unauthorized behavior. It can generate findings when an S3 bucket is made public, but it does not prevent the action from occurring. GuardDuty is a detective and response service, not a preventive control.
Quick Answer
The answer is Amazon S3 Block Public Access at the account level. This is the correct choice because it acts as a preventive control that overrides any bucket policies or ACLs that would grant public read or write access, applying automatically to all existing and newly created buckets across the entire AWS account without requiring individual bucket policy changes. On the AWS Certified Cloud Practitioner CLF-C02 exam, this question tests your understanding of the difference between detective and preventive controls, and the fact that account-level settings take precedence over bucket-level settings. A common trap is confusing this with bucket-level Block Public Access settings, which must be configured per bucket and do not enforce account-wide coverage. Remember the memory tip: account-level S3 Block Public Access is the "master switch" that locks down every bucket in the account, making it the only way to guarantee no bucket can ever be made public.
CLF-C02 Security and Compliance Practice Question
This CLF-C02 practice question tests your understanding of security and compliance. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company stores sensitive documents in Amazon S3. The security team wants a preventive control that ensures no S3 bucket in the AWS account can ever be configured with a bucket policy that grants public read or write access. This control must apply automatically to all newly created buckets and to existing buckets, without requiring changes to individual bucket policies. Which AWS feature should the security team use?
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
Amazon S3 Block Public Access at the account level
Amazon S3 Block Public Access at the account level is a preventive control that, when enabled, overrides any bucket policies or ACLs that would grant public read or write access. It applies automatically to all existing and newly created buckets in the account without requiring changes to individual bucket policies. This meets the security team's requirement for a blanket, account-wide preventive control.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
AWS Config with the s3-bucket-public-read-prohibited managed rule
Why it's wrong here
AWS Config is a detective service that evaluates resource configurations against rules. The s3-bucket-public-read-prohibited rule can detect buckets that allow public read access, but it does not prevent the bucket from being created or configured with public access. The scenario explicitly requires a preventive control, not a detective one.
- ✓
Amazon S3 Block Public Access at the account level
Why this is correct
Amazon S3 Block Public Access provides centralized controls that can be applied at the account level. When enabled, these settings override any bucket-level policies that grant public access, preventing both new and existing buckets from ever being made publicly accessible. This is the preventive control described in the scenario.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
AWS Identity and Access Management (IAM) policy with a condition that denies s3:PutBucketPolicy for any action that grants public access
Why it's wrong here
While an IAM policy with a condition key like s3:PutBucketPublicAccessBlock or a specific condition can deny PutBucketPolicy for public grants, it only applies to IAM users and roles that have the policy attached. It does not prevent the account root user or other authorized principals from making buckets public. It also does not apply to existing buckets that were made public before the policy was created. Therefore, it is not a comprehensive preventive control across the entire account.
- ✗
Amazon GuardDuty with a finding suppression rule for S3 public access events
Why it's wrong here
Amazon GuardDuty is a threat detection service that monitors for malicious activity and unauthorized behavior. It can generate findings when an S3 bucket is made public, but it does not prevent the action from occurring. GuardDuty is a detective and response service, not a preventive control.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse detective controls (like AWS Config rules) with preventive controls (like S3 Block Public Access), or they assume an IAM policy can universally block public access without considering that it must be attached to every principal and does not cover ACL-based public access.
Trap categories for this question
Scenario analysis trap
AWS Config is a detective service that evaluates resource configurations against rules. The s3-bucket-public-read-prohibited rule can detect buckets that allow public read access, but it does not prevent the bucket from being created or configured with public access. The scenario explicitly requires a preventive control, not a detective one.
Detailed technical explanation
How to think about this question
S3 Block Public Access at the account level works by applying four settings (BlockPublicAcls, IgnorePublicAcls, BlockPublicPolicy, RestrictPublicBuckets) that override any bucket-level permissions, including those set via bucket policies or ACLs. Under the hood, these settings are enforced at the S3 API layer, meaning any PutBucketPolicy or PutBucketAcl request that would result in public access is rejected with an AccessDenied error. This is particularly useful in multi-account environments where a centralized security team needs to enforce a no-public-access posture across all accounts.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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Security and Compliance — study guide chapter
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FAQ
Questions learners often ask
What does this CLF-C02 question test?
Security and Compliance — This question tests Security and Compliance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Amazon S3 Block Public Access at the account level — Amazon S3 Block Public Access at the account level is a preventive control that, when enabled, overrides any bucket policies or ACLs that would grant public read or write access. It applies automatically to all existing and newly created buckets in the account without requiring changes to individual bucket policies. This meets the security team's requirement for a blanket, account-wide preventive control.
What should I do if I get this CLF-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jun 11, 2026
This CLF-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 CLF-C02 exam.
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