The answer is to attach an IAM policy to the auditor’s IAM user that allows s3:ListBucket on the specific bucket. This is required because cross-account S3 access with IAM and bucket policies demands that both the resource-based policy (the bucket policy on the owning account) and the identity-based policy (on the auditor’s IAM user or role) explicitly grant the action—a principle often called the "AND" condition. On the AWS Certified Security Specialty SCS-C02 exam, this scenario tests your understanding that a bucket policy alone is insufficient when the request comes from a user in a different account; the user’s own account must also permit the operation. A common trap is assuming the bucket policy’s account-level grant covers all users in that account, but without an identity policy, the auditor’s user is still denied. Memory tip: think "both sides must say yes"—the bucket says yes, but the user’s IAM policy must also say yes for the action to proceed.
SCS-C02 Identity and Access Management Practice Question
This SCS-C02 practice question tests your understanding of identity and access management. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 uses cross-account IAM roles to allow a third-party auditor to access a specific S3 bucket. The auditor reports that they are getting 'Access Denied' errors when trying to list objects. The bucket policy allows access to the auditor's account. What additional configuration is needed?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Attach an IAM policy to the auditor's IAM user that allows s3:ListBucket on the specific bucket.
Option D is correct because cross-account access requires both the resource-based policy (bucket policy) and the identity-based policy (on the auditor's IAM user/role) to allow the action. Option A is wrong because the bucket policy already allows the account. Option B is wrong because SCPs are for the auditor's account, not the resource account. Option C is wrong because the trust policy is for assuming the role, not for S3 access.
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.
✗
Modify the trust policy of the IAM role to include the auditor's account.
Why it's wrong here
Trust policy is for assuming the role, not for S3 access.
✗
Ensure the auditor's account does not have a service control policy (SCP) denying S3 actions.
Why it's wrong here
While SCPs could block, the most common issue is missing IAM permission on the auditor's user.
✓
Attach an IAM policy to the auditor's IAM user that allows s3:ListBucket on the specific bucket.
Why this is correct
Cross-account access requires both the resource policy and the principal's IAM policy to allow the action.
Related concept
Standard ACLs match source addresses.
✗
Add a bucket policy that grants access to the auditor's IAM user ARN.
Why it's wrong here
The bucket policy already grants access to the account; the issue is missing permission on the auditor side.
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.
Identity and Access Management — This question tests Identity and Access Management — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Attach an IAM policy to the auditor's IAM user that allows s3:ListBucket on the specific bucket. — Option D is correct because cross-account access requires both the resource-based policy (bucket policy) and the identity-based policy (on the auditor's IAM user/role) to allow the action. Option A is wrong because the bucket policy already allows the account. Option B is wrong because SCPs are for the auditor's account, not the resource account. Option C is wrong because the trust policy is for assuming the role, not for S3 access.
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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