The correct answer is that a bucket ACL granting public read access overrides the policy condition, making the IP restriction ineffective. When an S3 bucket policy uses the `aws:SourceIp` condition to restrict access to a specific IP range, that condition is only evaluated if the request is not already allowed by a separate ACL. S3 evaluates both bucket policies and ACLs together, and if either grants access, the request succeeds—so a public-read ACL effectively bypasses the IP restriction. This scenario is a classic trap on the AWS Certified Advanced Networking Specialty ANS-C01 exam, testing your understanding of how S3 access control mechanisms interact: ACLs and bucket policies are additive, not hierarchical, and a permissive ACL can override a restrictive policy condition. A common memory tip is “ACL first, policy last—if ACL says yes, policy’s condition won’t last.”
ANS-C01 Network Security, Compliance and Governance Practice Question
This ANS-C01 practice question tests your understanding of network security, compliance and governance. 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.
Refer to the exhibit. A company has an S3 bucket policy that allows public read access only from a specific IP range (203.0.113.0/24). Users outside this range report that they can still access objects in the bucket. What is the most likely reason?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The bucket also has a bucket ACL that grants public read access, overriding the policy condition
Option C is correct. The condition key `aws:SourceIp` does not work if the request comes through an AWS service (e.g., CloudFront) because the source IP becomes the CloudFront IP. Also, if the bucket policy allows access via a pre-signed URL, the condition is not evaluated? Actually, pre-signed URLs bypass the bucket policy? No, pre-signed URLs still require the request to match the policy. However, the most common reason is that the bucket has an ACL that allows public access, overriding the policy. Option A is wrong because the bucket policy is evaluated. Option B is wrong because AWS does not use `aws:SourceIp` for requests made through an AWS service? The condition works for direct requests. Option D is wrong because the bucket is not encrypted. The most likely is that the bucket also has a bucket ACL that grants public access, and since ACLs are evaluated before bucket policies? Actually, ACLs and bucket policies are evaluated together, but if an ACL allows access, the policy condition might be ignored? No, the effective access is the union of all allowed permissions. So if ACL allows public access, the condition is irrelevant. Thus, option C is correct.
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.
✗
The bucket policy uses the wrong condition key; it should be aws:SourceIpAddress
Why it's wrong here
The correct condition key is aws:SourceIp.
✗
The bucket policy is not being evaluated because the bucket is in a different region
Why it's wrong here
Bucket policies are evaluated regardless of region.
✗
The bucket is configured with server-side encryption, which prevents the policy from being applied
Why it's wrong here
Encryption does not affect policy evaluation.
✓
The bucket also has a bucket ACL that grants public read access, overriding the policy condition
Why this is correct
ACLs can grant public access that bypasses the IP restriction in the bucket policy.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
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 ANS-C01 ACL questions on filtering logic and placement.
Network Security, Compliance and Governance — This question tests Network Security, Compliance and Governance — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: The bucket also has a bucket ACL that grants public read access, overriding the policy condition — Option C is correct. The condition key `aws:SourceIp` does not work if the request comes through an AWS service (e.g., CloudFront) because the source IP becomes the CloudFront IP. Also, if the bucket policy allows access via a pre-signed URL, the condition is not evaluated? Actually, pre-signed URLs bypass the bucket policy? No, pre-signed URLs still require the request to match the policy. However, the most common reason is that the bucket has an ACL that allows public access, overriding the policy. Option A is wrong because the bucket policy is evaluated. Option B is wrong because AWS does not use `aws:SourceIp` for requests made through an AWS service? The condition works for direct requests. Option D is wrong because the bucket is not encrypted. The most likely is that the bucket also has a bucket ACL that grants public access, and since ACLs are evaluated before bucket policies? Actually, ACLs and bucket policies are evaluated together, but if an ACL allows access, the policy condition might be ignored? No, the effective access is the union of all allowed permissions. So if ACL allows public access, the condition is irrelevant. Thus, option C is correct.
What should I do if I get this ANS-C01 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 ANS-C01 ACL questions on filtering logic and placement.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Standard ACLs match source addresses.
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