The answer is that the S3 bucket policy condition using IpAddress fails when users access the bucket through a VPC endpoint because the endpoint changes the source IP. When a VPC endpoint is used, the source IP of the request is not the client’s public or corporate IP but rather the private IP of the endpoint itself, which may fall outside the allowed 10.0.0.0/16 range specified in the condition. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of how VPC endpoints override source IP evaluation in bucket policies—a common trap where candidates assume the client’s IP is always visible. The key distinction is that VPC endpoints use the endpoint’s network interface IP, not the original requester’s IP, making IpAddress conditions ineffective for traffic routed through them. Memory tip: “Endpoint IP replaces client IP—if you use IpAddress, your policy will slip.”
SCS-C02 Infrastructure Security Practice Question
This SCS-C02 practice question tests your understanding of infrastructure security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 has the S3 bucket policy shown in the exhibit. The bucket contains sensitive data that should only be accessible from within the corporate network (10.0.0.0/16). However, users inside the corporate network report that they cannot access objects in the bucket. What is the most likely cause?
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
✓
Users are accessing the bucket through a VPC endpoint, which changes the source IP.
Option B is correct because the condition uses IpAddress, which evaluates the source IP of the request. If users are accessing via a VPC endpoint, the source IP is not the client IP but the endpoint's private IP, which may not be in the specified range. Option A is wrong because a condition exists. Option C is wrong because IAM roles are not relevant to the public policy. Option D is wrong because SSL is not required by the policy.
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.
✗
Users do not have the appropriate IAM role assigned.
Why it's wrong here
The bucket policy grants public access; IAM is not needed.
✓
Users are accessing the bucket through a VPC endpoint, which changes the source IP.
Why this is correct
VPC endpoints use private IPs; the IpAddress condition may not match.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
✗
The policy does not have a Deny statement.
Why it's wrong here
Allow statements are sufficient; a Deny is not required.
✗
The bucket policy requires SSL but the connection is not using HTTPS.
Why it's wrong here
The policy does not require SSL; it only checks IP.
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: Users are accessing the bucket through a VPC endpoint, which changes the source IP. — Option B is correct because the condition uses IpAddress, which evaluates the source IP of the request. If users are accessing via a VPC endpoint, the source IP is not the client IP but the endpoint's private IP, which may not be in the specified range. Option A is wrong because a condition exists. Option C is wrong because IAM roles are not relevant to the public policy. Option D is wrong because SSL is not required by the policy.
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.
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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