- A
Verify that the security group associated with the VPC endpoint allows inbound traffic.
Why wrong: Security groups are not applicable to gateway endpoints.
- B
Check the VPC endpoint policy to ensure it allows the actions the users are performing.
The endpoint policy might be restrictive.
- C
Check that the route table for the subnets has a route to the VPC endpoint.
Without a route, traffic may not go through the endpoint.
- D
Ensure the VPC endpoint is in the same region as the S3 bucket.
Why wrong: S3 endpoints are region-specific; this is a basic requirement, not a troubleshooting step.
- E
Verify that the bucket policy includes a condition that denies access if the source VPC endpoint is not the specified one.
Without a deny condition, the policy may allow other access.
Quick Answer
The answer is to verify the bucket policy includes a condition key that denies access when the source VPC endpoint does not match the specified one, because a bucket policy that only allows access from a VPC endpoint is insufficient—it must explicitly deny all other traffic to enforce the restriction. This is a common misconfiguration when troubleshooting S3 VPC endpoint bucket policy issues, as an allow-only policy can be overridden by other IAM permissions, leaving the bucket accessible from outside the VPC. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding of the difference between explicit allow and explicit deny in resource-based policies, often appearing as a trap where candidates forget that an allow statement alone does not block other access. A reliable memory tip is “Deny to lock, allow to talk”—always include a Deny condition for the specific VPC endpoint ID to lock down access, then allow the necessary actions through the endpoint policy and route table.
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 an Amazon S3 bucket with a bucket policy that restricts access to a specific VPC endpoint. However, users are still able to access the bucket from outside the VPC. Which THREE steps should the security engineer take to troubleshoot this issue? (Choose THREE.)
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
Check the VPC endpoint policy to ensure it allows the actions the users are performing.
Option A is correct because the bucket policy must explicitly deny access from outside the VPC endpoint. Option C is correct because the VPC endpoint policy must allow the required actions. Option E is correct because the route table must include a route to the S3 endpoint. Option B is wrong because the VPC endpoint must be in the same region. Option D is wrong because security groups are not required for S3 endpoint access.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Verify that the security group associated with the VPC endpoint allows inbound traffic.
Why it's wrong here
Security groups are not applicable to gateway endpoints.
- ✓
Check the VPC endpoint policy to ensure it allows the actions the users are performing.
Why this is correct
The endpoint policy might be restrictive.
Related concept
CIDR notation defines the prefix length.
- ✓
Check that the route table for the subnets has a route to the VPC endpoint.
Why this is correct
Without a route, traffic may not go through the endpoint.
Related concept
CIDR notation defines the prefix length.
- ✗
Ensure the VPC endpoint is in the same region as the S3 bucket.
Why it's wrong here
S3 endpoints are region-specific; this is a basic requirement, not a troubleshooting step.
- ✓
Verify that the bucket policy includes a condition that denies access if the source VPC endpoint is not the specified one.
Why this is correct
Without a deny condition, the policy may allow other access.
Related concept
CIDR notation defines the prefix length.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
- CIDR notation defines the prefix length.
- Block size helps identify subnet boundaries.
- Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
- The required host count determines the smallest suitable subnet.
TExam Day Tips
- Write the block size before choosing the subnet.
- Check whether the question asks for hosts, subnets or a specific address range.
- Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SCS-C02 subnetting questions on CIDR, address ranges, and subnet selection.
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FAQ
Questions learners often ask
What does this SCS-C02 question test?
Infrastructure Security — This question tests Infrastructure Security — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Check the VPC endpoint policy to ensure it allows the actions the users are performing. — Option A is correct because the bucket policy must explicitly deny access from outside the VPC endpoint. Option C is correct because the VPC endpoint policy must allow the required actions. Option E is correct because the route table must include a route to the S3 endpoint. Option B is wrong because the VPC endpoint must be in the same region. Option D is wrong because security groups are not required for S3 endpoint access.
What should I do if I get this SCS-C02 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SCS-C02 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
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Last reviewed: Jun 20, 2026
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.
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