This SCS-C02 practice question tests your understanding of infrastructure security. 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.
A company uses AWS Organizations with multiple accounts. The security team wants to ensure that all new member accounts automatically deny public access to S3 buckets. Which policy should be attached to the root organizational unit?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Attach a service control policy (SCP) to the root OU
Option C is correct because an SCP can deny public access to S3 buckets across all accounts in the organization. Option A is wrong because an IAM policy only applies to IAM users/groups/roles, not accounts. Option B is wrong because a bucket policy is per-bucket, not across accounts. Option D is wrong because a trust policy is for IAM roles, not S3 access control.
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.
✗
Attach an S3 bucket policy to each bucket
Why it's wrong here
Bucket policies are per-bucket and would need to be applied manually to each new account.
✗
Attach an IAM policy to the root user
Why it's wrong here
IAM policies apply to IAM principals, not to S3 bucket policies across accounts.
✗
Attach a trust policy to the OrganizationAccountAccessRole
Why it's wrong here
Trust policies control cross-account role assumptions, not S3 public access settings.
✓
Attach a service control policy (SCP) to the root OU
Why this is correct
SCPs can set permission boundaries across entire accounts, denying actions like s3:PutBucketPublicAccessBlock.
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 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: Attach a service control policy (SCP) to the root OU — Option C is correct because an SCP can deny public access to S3 buckets across all accounts in the organization. Option A is wrong because an IAM policy only applies to IAM users/groups/roles, not accounts. Option B is wrong because a bucket policy is per-bucket, not across accounts. Option D is wrong because a trust policy is for IAM roles, not S3 access control.
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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