The correct answer is to create an Origin Access Identity (OAI) and add a bucket policy that grants access only to that OAI. This configuration works because the OAI is a special CloudFront user that authenticates the distribution to the S3 bucket; when you attach a bucket policy that explicitly denies all principals except the OAI, direct requests to the S3 endpoint are blocked, while requests routed through CloudFront are allowed. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding of securing an S3 bucket as a CloudFront origin, and a common trap is confusing signed URLs (which control viewer access) with OAI (which controls origin access). Remember that OAI locks down the origin, not the viewer. A helpful memory tip: OAI stands for “Only Access from Inside” CloudFront—think of it as a secret handshake between CloudFront and S3 that no one else can use.
SOA-C02 Networking and Content Delivery Practice Question
This SOA-C02 practice question tests your understanding of networking and content delivery. 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 has a CloudFront distribution with an S3 bucket as the origin. The S3 bucket contains sensitive data that should only be accessible through CloudFront. Which configuration is required to ensure that direct access to the S3 bucket is blocked?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create an Origin Access Identity (OAI) and add a bucket policy that grants access only to the OAI
Option A is correct because Origin Access Identity (OAI) prevents direct S3 access by allowing only CloudFront to access the bucket. Option B is wrong because signed URLs control viewer access, not origin access. Option C is wrong because bucket policies alone can restrict access, but OAI is the standard way. Option D is wrong because CloudFront does not use IAM roles for origin 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.
✗
Attach an IAM role to CloudFront that allows S3 access
Why it's wrong here
CloudFront does not support IAM roles for origin access; it uses OAI.
✗
Set the S3 bucket policy to deny all access except from CloudFront's IP ranges
Why it's wrong here
CloudFront IP ranges change and are not recommended; OAI is more secure.
✓
Create an Origin Access Identity (OAI) and add a bucket policy that grants access only to the OAI
Why this is correct
The OAI is a virtual identity that CloudFront uses to access S3; the bucket policy restricts access to only that OAI.
Related concept
Standard ACLs match source addresses.
✗
Use signed URLs for all requests
Why it's wrong here
Signed URLs restrict viewer access but do not block direct S3 access if the bucket is public.
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 SOA-C02 ACL questions on filtering logic and placement.
Networking and Content Delivery — This question tests Networking and Content Delivery — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Create an Origin Access Identity (OAI) and add a bucket policy that grants access only to the OAI — Option A is correct because Origin Access Identity (OAI) prevents direct S3 access by allowing only CloudFront to access the bucket. Option B is wrong because signed URLs control viewer access, not origin access. Option C is wrong because bucket policies alone can restrict access, but OAI is the standard way. Option D is wrong because CloudFront does not use IAM roles for origin access.
What should I do if I get this SOA-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 SOA-C02 ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
About these practice questions
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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. Refer to the exhibit. An S3 bucket policy is configured for a CloudFront distribution using an OAI. The policy allows the OAI to get objects. Additionally, it allows anyone from the IP range 203.0.113.0/24 to get objects directly. Users from other IPs report they can still access objects directly via S3 URLs. What is the most likely cause?
hard
A.The policy allows public access from the specified IP range, overriding the OAI restriction.
B.The OAI is not correctly associated with the CloudFront distribution.
C.The CloudFront distribution is using a custom origin instead of S3.
✓ D.The S3 bucket has a bucket ACL that grants public read access.
Why D: Option C is correct because the policy allows the OAI, but the second statement allows all principals from a specific IP. The issue is that the policy does not explicitly deny public access; it only allows the OAI and a specific IP range. However, the OAI statement allows the OAI, but if the bucket is not properly configured to block public access, the default may allow public read. Actually, the bucket policy has two Allow statements. The second statement allows all principals from the IP range, but for other IPs, there is no explicit allow or deny. The default is implicit deny, so other IPs should not have access. However, the exhibit shows that users from other IPs can still access. This suggests that the bucket ACL might allow public read, or the bucket policy is not the only access control. Option A is wrong because the OAI is specified. Option B is wrong because the OAI is allowed. Option D is wrong because the policy is valid.
Variation 2. Which TWO methods can be used to secure an S3 bucket that is used as an origin for Amazon CloudFront? (Select two.)
medium
✓ A.Write a bucket policy that allows only the CloudFront distribution’s OAI.
B.Use bucket ACLs to grant public read access.
C.Enable S3 server-side encryption.
✓ D.Configure an origin access identity (OAI) and restrict bucket access.
E.Generate pre-signed URLs for all objects.
Why A: Option A is correct because OAI ensures only CloudFront can access the bucket. Option C is correct because a bucket policy can restrict access to CloudFront. Option B is wrong because bucket ACLs are legacy. Option D is wrong because pre-signed URLs grant temporary access, not a security method for the origin. Option E is wrong because encryption protects data at rest, not access control.
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