SCS-C02 Infrastructure Security Practice Question
A security engineer needs to ensure that an Amazon S3 bucket blocks all public access. Which S3 block public access settings should be enabled?
⚠ Common exam trap
Many exam-takers think enabling individual settings (like blocking new bucket policies or new ACLs) is sufficient, but they overlook that existing policies or ACLs could still allow public access, and only 'Block all public access' guarantees complete closure of all public access vectors.
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
✓
Block all public access
The 'Block all public access' setting in Amazon S3 is a single toggle that simultaneously enables all four individual block public access settings, ensuring that no public access is allowed through any mechanism—bucket policies, ACLs, or otherwise. This is the only setting that comprehensively blocks all public access to the S3 bucket and its objects, as required by the security engineer's goal.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Block public access to buckets and objects granted through new public bucket policies
Why it's wrong here
This option maps to the BlockPublicPolicy S3 Block Public Access setting. It only prevents attaching a new bucket policy that grants public access, so a public bucket policy that was already in place remains active and can continue to permit anonymous requests. It also does nothing to restrain public ACLs, meaning existing ACLs may still grant public access. Therefore, this single setting cannot guarantee that the bucket is private.
- ✗
Block public access to buckets and objects granted through new access control lists (ACLs)
Why it's wrong here
This option is the BlockPublicAcls control. It blocks creation of new public bucket or object ACLs and prevents uploading objects with public ACLs, but it leaves any public ACLs that already exist fully effective. It additionally provides no protection against public bucket policies, and as long as either an existing public ACL or a public bucket policy is present, the bucket can still be publicly accessible. Thus it only addresses future ACL-based exposure.
- ✗
Block public access to buckets and objects granted through any access control lists (ACLs)
Why it's wrong here
This option corresponds to the IgnorePublicAcls control. When enabled, S3 ignores all public ACLs, including existing ones, by removing their effect from the access evaluation. However, it does not evaluate or restrict bucket policies, so a bucket policy with a Principal of "*" or an explicit public grant can still allow anonymous access. Since public access can persist purely through a bucket policy, this setting alone is insufficient to make the bucket private.
- ✓
Block all public access
Why this is correct
This option enables all four S3 Block Public Access settings: BlockPublicAcls, IgnorePublicAcls, BlockPublicPolicy, and RestrictPublicBuckets. BlockPublicAcls stops new public ACLs, IgnorePublicAcls causes existing public ACLs to be disregarded, BlockPublicPolicy prevents adding new public bucket policies, and RestrictPublicBuckets limits how existing public policies are used. Together they close both ACL-based and bucket-policy-based pathways for anonymous or public access, making this the correct choice to ensure the bucket is not publicly accessible.
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 SCS-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 SCS-C02 exam.