The correct answer is to enable all four S3 block public access settings, which collectively block any public access granted through bucket policies, access control lists (ACLs), or any other method. This works by applying the most restrictive combination of controls: blocking new public ACLs and bucket policies, removing existing public ACLs and policies, and ignoring any public ACLs that might still be attached. On the AWS Certified Security Specialty SCS-C02 exam, this concept tests your understanding of the layered security model for S3, where a common trap is assuming that enabling just one or two settings is sufficient to fully lock down a bucket. The exam often presents scenarios where a security engineer must guarantee zero public exposure, and the only foolproof answer is the “Block all public access” toggle, which activates all four individual settings. Memory tip: think of it as the “four-way deadbolt” — you must turn all four locks to fully secure the door, because leaving even one unlocked leaves a gap for public access.
SCS-C02 Infrastructure Security Practice Question
This SCS-C02 practice question tests your understanding of infrastructure security. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 security engineer needs to ensure that an Amazon S3 bucket blocks all public access. Which S3 block public access settings should be enabled?
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 correct answer is D because enabling all four block public access settings provides the most restrictive public access controls. Option A is wrong because it only blocks access that is granted to the public via bucket policies or ACLs, but not all public access. Option B is wrong because it only blocks access that is granted to the public via ACLs. Option C is wrong because it only blocks access that is granted to the public via bucket policies.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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 setting blocks new public bucket policies, but existing policies or ACLs may still allow public access.
✗
Block public access to buckets and objects granted through new access control lists (ACLs)
Why it's wrong here
This setting only blocks new public ACLs, but existing public ACLs or bucket policies may still allow public access.
✗
Block public access to buckets and objects granted through any access control lists (ACLs)
Why it's wrong here
This setting blocks public ACLs, but bucket policies could still grant public access.
✓
Block all public access
Why this is correct
This setting blocks all public access, including both ACLs and bucket policies.
Related concept
Standard ACLs match source addresses.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related SCS-C02 ACL questions on filtering logic and placement.
Infrastructure Security — This question tests Infrastructure Security — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Block all public access — The correct answer is D because enabling all four block public access settings provides the most restrictive public access controls. Option A is wrong because it only blocks access that is granted to the public via bucket policies or ACLs, but not all public access. Option B is wrong because it only blocks access that is granted to the public via ACLs. Option C is wrong because it only blocks access that is granted to the public via bucket policies.
What should I do if I get this SCS-C02 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related SCS-C02 ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
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Question Discussion
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