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Question 1,014 of 1,738

Identity and Access Management →hardMultiple ChoiceObjective-mapped

Quick Answer

The answer is updating the bucket ACL to grant the CloudTrail service write access, because CloudTrail log delivery requires both a valid bucket policy and a compatible bucket ACL. While the bucket policy correctly restricts PutObject to the source account via the aws:SourceAccount condition, CloudTrail first performs a GetBucketAcl call to verify bucket ownership, and if the bucket ACL does not explicitly grant the CloudTrail service principal the necessary permissions, the delivery fails regardless of the policy. This question tests your understanding of the interaction between S3 bucket policies and ACLs in the context of centralized logging, a common scenario on the AWS Certified Security Specialty SCS-C02 exam where candidates often assume a policy alone is sufficient. The trap is that CloudTrail does not use IAM roles for log delivery—it relies on its own service principal and checks the ACL as an additional authorization layer. Memory tip: CloudTrail checks the ACL first, so think “ACL before policy” for log delivery success.

SCS-C02 Identity and Access Management Practice Question

This SCS-C02 practice question tests your understanding of identity and access management. 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 a multi-account AWS organization with centralized logging in a Security account. The Security account contains an S3 bucket that stores CloudTrail logs from all member accounts. The bucket policy allows CloudTrail from member accounts to deliver logs. Recently, a security audit revealed that the bucket is publicly accessible. The security engineer must ensure that only authorized accounts can access the logs. The engineer updates the bucket policy to include a condition that restricts access to specific AWS accounts. However, after the change, member accounts report that CloudTrail is failing to deliver logs to the bucket. The bucket policy currently includes the following statement: { "Effect": "Allow", "Principal": "*", "Action": "s3:PutObject", "Resource": "arn:aws:s3:::central-logs/*", "Condition": { "StringEquals": { "aws:SourceAccount": "111111111111" } } } The Security account ID is 222222222222. What is the MOST likely cause of the delivery failure, and what should the engineer do to fix it?

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.

Question 1hardmultiple choice

Full question →

A
Modify the KMS key policy to allow CloudTrail to decrypt and re-encrypt logs if SSE-KMS is enabled.
Why wrong: Incorrect: The question does not mention KMS; the error is about bucket ACL.
B
Update the bucket ACL to grant the CloudTrail service write access, as CloudTrail requires both bucket policy and ACL permissions.
Correct: CloudTrail checks bucket ACL for PutObject; the bucket ACL must allow CloudTrail to write.
C
Change the Principal from "*" to the CloudTrail service principal to restrict access more tightly.
Why wrong: Incorrect: The Principal already allows delivery; the issue is the bucket ACL.
D
Create an IAM role in the Security account and configure member accounts to use that role for log delivery.
Why wrong: Incorrect: CloudTrail does not use an IAM role for cross-account log delivery; it uses a service principal.

Full breakdown with real-world context →

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

✓

Update the bucket ACL to grant the CloudTrail service write access, as CloudTrail requires both bucket policy and ACL permissions.

Option B is correct because CloudTrail uses GetBucketAcl to verify bucket ownership. The bucket ACL must grant the CloudTrail service access, but the bucket ACL is separate from the bucket policy. The error suggests that the bucket ACL does not grant CloudTrail the necessary permissions. Option A is incorrect because the bucket policy already allows PutObject. Option C is incorrect because CloudTrail does not need to assume a role for log delivery; it uses its own service principal. Option D is incorrect because the issue is not related to KMS key policy but to bucket ACL.

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 KMS key policy to allow CloudTrail to decrypt and re-encrypt logs if SSE-KMS is enabled.
Why it's wrong here
Incorrect: The question does not mention KMS; the error is about bucket ACL.
✓
Update the bucket ACL to grant the CloudTrail service write access, as CloudTrail requires both bucket policy and ACL permissions.
Why this is correct
Correct: CloudTrail checks bucket ACL for PutObject; the bucket ACL must allow CloudTrail to write.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
✗
Change the Principal from "*" to the CloudTrail service principal to restrict access more tightly.
Why it's wrong here
Incorrect: The Principal already allows delivery; the issue is the bucket ACL.
✗
Create an IAM role in the Security account and configure member accounts to use that role for log delivery.
Why it's wrong here
Incorrect: CloudTrail does not use an IAM role for cross-account log delivery; it uses a service principal.

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.

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FAQ

Questions learners often ask

What does this SCS-C02 question test?

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: Update the bucket ACL to grant the CloudTrail service write access, as CloudTrail requires both bucket policy and ACL permissions. — Option B is correct because CloudTrail uses GetBucketAcl to verify bucket ownership. The bucket ACL must grant the CloudTrail service access, but the bucket ACL is separate from the bucket policy. The error suggests that the bucket ACL does not grant CloudTrail the necessary permissions. Option A is incorrect because the bucket policy already allows PutObject. Option C is incorrect because CloudTrail does not need to assume a role for log delivery; it uses its own service principal. Option D is incorrect because the issue is not related to KMS key policy but to bucket ACL.

What should I do if I get this SCS-C02 question wrong?

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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Same concept, more angles

1 more ways this is tested on SCS-C02

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. A company has a multi-account AWS Organizations setup with a central security account (Account ID: 111122223333) and several member accounts. The security team uses AWS CloudTrail to log all API calls across accounts and stores the logs in an S3 bucket (my-cloudtrail-bucket) in the security account. The team wants to allow the security team members (IAM users in the security account) to access the CloudTrail logs, while denying access to all other users in the organization, including the root user of the security account. The security team has attached the following IAM policy to the IAM group containing the security team members: { "Version": "2012-10-17", "Statement": [ { "Effect": "Allow", "Action": "s3:GetObject", "Resource": "arn:aws:s3:::my-cloudtrail-bucket/*" } ] } However, a security team member reports that they are receiving an AccessDenied error when trying to download a log file. The bucket policy is as follows: { "Version": "2012-10-17", "Statement": [ { "Effect": "Deny", "Principal": "*", "Action": "s3:GetObject", "Resource": "arn:aws:s3:::my-cloudtrail-bucket/*", "Condition": { "Bool": { "aws:SecureTransport": "false" } } }, { "Effect": "Allow", "Principal": { "AWS": "arn:aws:iam::111122223333:root" }, "Action": "s3:GetObject", "Resource": "arn:aws:s3:::my-cloudtrail-bucket/*" }, { "Effect": "Deny", "Principal": "*", "Action": "s3:*", "Resource": "arn:aws:s3:::my-cloudtrail-bucket/*", "Condition": { "StringNotEquals": { "aws:PrincipalAccount": "111122223333" } } } ] } What is the most likely reason for the AccessDenied error?

hard

A.The bucket policy denies access to all principals except those in account 111122223333, but the IAM users are in that account, so they are denied.
B.The bucket policy requires secure transport, and the security team member is not using HTTPS.
✓ C.The bucket policy allows only the root user of the security account, not the IAM users.
D.The IAM policy has an implicit deny because the security team members are not allowed to access S3.

Why C: Option B is correct. The bucket policy allows the root user but does not explicitly allow the IAM users. While the root user is allowed, the Deny statement for non-root users is not present; however, the Allow for root does not extend to IAM users. The IAM users are not the root user, so the Allow statement does not apply to them. The IAM policy allows GetObject, but the bucket policy does not grant access to the IAM users, so the default implicit deny applies. Option A is wrong because the IAM policy does not have a Deny. Option C is wrong because the Deny for non-111122223333 accounts does not affect users in the same account. Option D is wrong because the SecureTransport condition only denies when HTTPS is not used.

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