← SOA-C02·Amazon Web Services

Question 1,299 of 1,546

Networking and Content Delivery →mediumMultiple SelectObjective-mapped

Two Methods to Block Direct S3 Access When Using CloudFront

This SOA-C02 practice question tests your understanding of networking and content delivery. 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.

Which TWO methods can be used to secure an S3 bucket that is used as an origin for Amazon CloudFront? (Select two.)

A
Write a bucket policy that allows only the CloudFront distribution’s OAI.
Bucket policy can restrict access to the OAI.
B
Use bucket ACLs to grant public read access.
Why wrong: Public read access defeats security.
C
Enable S3 server-side encryption.
Why wrong: Encryption protects data at rest, not access control.
D
Configure an origin access identity (OAI) and restrict bucket access.
OAI ensures only CloudFront can access the bucket.
E
Generate pre-signed URLs for all objects.
Why wrong: Pre-signed URLs grant time-limited access, not suitable for origin protection.

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

✓

Write a bucket policy that allows only the CloudFront distribution’s OAI.

Option A is correct because a bucket policy that grants access only to the CloudFront distribution's OAI ensures that only CloudFront can retrieve objects, preventing direct public access. Option D is correct because configuring an origin access identity (OAI) and restricting bucket access is the standard method to secure the S3 origin. Option B is incorrect because granting public read access via bucket ACLs would allow anyone to access the bucket, defeating security. Option C is incorrect because S3 server-side encryption protects data at rest but does not control access to the bucket. Option E is incorrect because pre-signed URLs provide temporary access to individual objects but are not a method to secure the origin bucket itself.

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.

✓
Write a bucket policy that allows only the CloudFront distribution’s OAI.
Why this is correct
Bucket policy can restrict access to the OAI.
Related concept
Standard ACLs match source addresses.
✗
Use bucket ACLs to grant public read access.
Why it's wrong here
Public read access defeats security.
✗
Enable S3 server-side encryption.
Why it's wrong here
Encryption protects data at rest, not access control.
✓
Configure an origin access identity (OAI) and restrict bucket access.
Why this is correct
OAI ensures only CloudFront can access the bucket.
Related concept
Standard ACLs match source addresses.
✗
Generate pre-signed URLs for all objects.
Why it's wrong here
Pre-signed URLs grant time-limited access, not suitable for origin protection.

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.

Visual reference

Quick reference

AWS S3 Storage Class Comparison

Storage Class	Min Duration	Retrieval	Use Case
S3 Standard	None	Immediate	Frequently accessed data
S3 Standard-IA	30 days	Immediate	Infrequent access, rapid retrieval
S3 One Zone-IA	30 days	Immediate	Non-critical infrequent data
S3 Intelligent-Tiering	None	Immediate–hours	Unknown or changing access patterns
S3 Glacier Instant	90 days	Milliseconds	Archive with instant retrieval
S3 Glacier Flexible	90 days	Minutes–hours	Archive, flexible retrieval
S3 Glacier Deep Archive	180 days	Hours	Long-term compliance archive

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.

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FAQ

Questions learners often ask

What does this SOA-C02 question test?

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: Write a bucket policy that allows only the CloudFront distribution’s OAI. — Option A is correct because a bucket policy that grants access only to the CloudFront distribution's OAI ensures that only CloudFront can retrieve objects, preventing direct public access. Option D is correct because configuring an origin access identity (OAI) and restricting bucket access is the standard method to secure the S3 origin. Option B is incorrect because granting public read access via bucket ACLs would allow anyone to access the bucket, defeating security. Option C is incorrect because S3 server-side encryption protects data at rest but does not control access to the bucket. Option E is incorrect because pre-signed URLs provide temporary access to individual objects but are not a method to secure the origin bucket itself.

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

What is the key concept behind this question?

Standard ACLs match source addresses.

About these practice questions

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Same concept, more angles

2 more ways this is tested on SOA-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 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?

medium

A.Attach an IAM role to CloudFront that allows S3 access
B.Set the S3 bucket policy to deny all access except from CloudFront's IP ranges
✓ C.Create an Origin Access Identity (OAI) and add a bucket policy that grants access only to the OAI
D.Use signed URLs for all requests

Why C: Option C is correct because Origin Access Identity (OAI) prevents direct S3 access by allowing only CloudFront to access the bucket. Option A is wrong because IAM roles are not used for origin access in CloudFront. Option B is wrong because CloudFront IP ranges change and are not a reliable method. Option D is wrong because signed URLs control viewer access, not origin access.

Variation 2. 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: The bucket policy has two Allow statements: one for the OAI and one for the IP range 203.0.113.0/24. For users from other IPs, there is no explicit Allow, so by default the policy implicitly denies access. However, S3 also evaluates bucket ACLs independently. If the bucket ACL grants public read access (e.g., AllUsers with READ permission), then users from any IP can access objects directly via S3 URLs, regardless of the bucket policy. Therefore, the most likely cause is that the bucket has a public-read ACL, which overrides the implicit deny in the policy.

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