- A
Associate an AWS WAF web ACL with the CloudFront distribution.
CloudFront supports AWS WAF at the edge, so requests can be inspected and filtered before they reach the origin. This placement stops malicious traffic early and applies the protection globally at the distribution layer.
- B
Restrict the ALB security group inbound rules to the AWS-managed CloudFront origin-facing prefix list.
Limiting the ALB security group to the CloudFront origin-facing prefix list ensures the load balancer only accepts traffic from CloudFront edge-to-origin connections. That blocks direct client access from the internet while still allowing CloudFront to forward legitimate requests to the application.
- C
Place the ALB in private subnets and keep the CloudFront distribution unchanged.
Why wrong: A standard internet-facing CloudFront distribution needs a reachable origin. Simply moving the ALB to private subnets does not provide a valid direct origin path for CloudFront and does not satisfy the requirement by itself.
- D
Use an S3 Origin Access Control instead of a security group change.
Why wrong: Origin Access Control is an S3-origin feature and does not apply to an ALB. It cannot restrict traffic to a load balancer origin or replace security group controls.
- E
Open the ALB to 0.0.0.0/0 and rely on WAF alone for protection.
Why wrong: WAF can filter requests, but leaving the ALB open to the internet violates the requirement to prevent direct access to the origin. The origin must be restricted at the network layer so only CloudFront can reach it.
SAA-C03 Design Secure Architectures Practice Question
This SAA-C03 practice question tests your understanding of design secure architectures. 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 public web application sits behind Amazon CloudFront with an Application Load Balancer as the origin. The security team wants all edge traffic inspected by AWS WAF and also wants to prevent anyone on the internet from reaching the ALB directly. Which two changes should be made? Select two.
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
Associate an AWS WAF web ACL with the CloudFront distribution.
Option A is correct because AWS WAF can be associated directly with a CloudFront distribution to inspect all edge traffic before it reaches the origin. This allows the security team to filter malicious requests at the AWS edge locations, reducing the attack surface and offloading processing from the Application Load Balancer.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Associate an AWS WAF web ACL with the CloudFront distribution.
Why this is correct
CloudFront supports AWS WAF at the edge, so requests can be inspected and filtered before they reach the origin. This placement stops malicious traffic early and applies the protection globally at the distribution layer.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Restrict the ALB security group inbound rules to the AWS-managed CloudFront origin-facing prefix list.
Why this is correct
Limiting the ALB security group to the CloudFront origin-facing prefix list ensures the load balancer only accepts traffic from CloudFront edge-to-origin connections. That blocks direct client access from the internet while still allowing CloudFront to forward legitimate requests to the application.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Place the ALB in private subnets and keep the CloudFront distribution unchanged.
Why it's wrong here
A standard internet-facing CloudFront distribution needs a reachable origin. Simply moving the ALB to private subnets does not provide a valid direct origin path for CloudFront and does not satisfy the requirement by itself.
When this WOULD be correct
If the origin were an internal ALB behind a VPN or Direct Connect, and CloudFront was configured with a custom origin using a public DNS name that resolves to the ALB's private IP via a custom domain, then placing the ALB in private subnets would be correct to prevent direct internet access.
- ✗
Use an S3 Origin Access Control instead of a security group change.
Why it's wrong here
Origin Access Control is an S3-origin feature and does not apply to an ALB. It cannot restrict traffic to a load balancer origin or replace security group controls.
When this WOULD be correct
In a scenario where the origin is an S3 bucket hosting a static website behind CloudFront, and the requirement is to prevent direct access to the bucket, using S3 Origin Access Control (or OAI) would be correct.
- ✗
Open the ALB to 0.0.0.0/0 and rely on WAF alone for protection.
Why it's wrong here
WAF can filter requests, but leaving the ALB open to the internet violates the requirement to prevent direct access to the origin. The origin must be restricted at the network layer so only CloudFront can reach it.
When this WOULD be correct
If the question required allowing direct internet access to the ALB while still using WAF, and the ALB security group was the only way to apply WAF (e.g., no CloudFront), then opening to 0.0.0.0/0 with WAF on the ALB would be correct.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The SAA-C03 exam frequently reuses these exact scenarios with slightly different constraints.
✓Associate an AWS WAF web ACL with the CloudFront distribution.Correct answer▾
Why this is correct
CloudFront supports AWS WAF at the edge, so requests can be inspected and filtered before they reach the origin. This placement stops malicious traffic early and applies the protection globally at the distribution layer.
✗Place the ALB in private subnets and keep the CloudFront distribution unchanged.Wrong answer — click to see why▾
Why this is wrong here
Placing the ALB in private subnets prevents CloudFront from reaching it because CloudFront cannot access private subnets directly; the ALB must be internet-facing or in public subnets with proper security group rules to allow CloudFront traffic.
★ When this WOULD be the correct answer
If the origin were an internal ALB behind a VPN or Direct Connect, and CloudFront was configured with a custom origin using a public DNS name that resolves to the ALB's private IP via a custom domain, then placing the ALB in private subnets would be correct to prevent direct internet access.
Why candidates choose this
Candidates know that private subnets block direct internet access, so they assume this automatically secures the ALB, but they overlook that CloudFront needs network-level access to the ALB, which private subnets without proper routing or security group rules would block.
✗Use an S3 Origin Access Control instead of a security group change.Wrong answer — click to see why▾
Why this is wrong here
S3 Origin Access Control (OAC) is used to restrict access to an S3 bucket origin, not an ALB. The question specifies an ALB as the origin, so OAC does not apply.
★ When this WOULD be the correct answer
In a scenario where the origin is an S3 bucket hosting a static website behind CloudFront, and the requirement is to prevent direct access to the bucket, using S3 Origin Access Control (or OAI) would be correct.
Why candidates choose this
Candidates may confuse S3 OAC with a general access control mechanism for all origins, or they might misread the question as involving an S3 origin instead of an ALB.
✗Open the ALB to 0.0.0.0/0 and rely on WAF alone for protection.Wrong answer — click to see why▾
Why this is wrong here
Opening the ALB to 0.0.0.0/0 allows direct internet access, bypassing CloudFront and WAF inspection, violating the requirement to prevent direct ALB access.
★ When this WOULD be the correct answer
If the question required allowing direct internet access to the ALB while still using WAF, and the ALB security group was the only way to apply WAF (e.g., no CloudFront), then opening to 0.0.0.0/0 with WAF on the ALB would be correct.
Why candidates choose this
Candidates may think WAF alone provides sufficient protection, overlooking the need to enforce traffic through CloudFront to meet the 'no direct ALB access' requirement.
Analysis generated from the official SAA-C03blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often think placing the ALB in private subnets is sufficient, but they forget that CloudFront cannot route traffic to private subnets without a public endpoint or a VPC origin configuration, making option C invalid.
Detailed technical explanation
How to think about this question
AWS WAF integrates with CloudFront at the edge, inspecting HTTP(S) requests before they traverse the AWS backbone to the origin. The ALB security group should reference the AWS-managed prefix list for CloudFront (com.amazonaws.global.cloudfront.origin-facing) to allow only traffic from CloudFront’s IP ranges, which are dynamically updated by AWS. This ensures that even if someone discovers the ALB’s DNS name, they cannot bypass CloudFront and WAF protections.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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
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FAQ
Questions learners often ask
What does this SAA-C03 question test?
Design Secure Architectures — This question tests Design Secure Architectures — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Associate an AWS WAF web ACL with the CloudFront distribution. — Option A is correct because AWS WAF can be associated directly with a CloudFront distribution to inspect all edge traffic before it reaches the origin. This allows the security team to filter malicious requests at the AWS edge locations, reducing the attack surface and offloading processing from the Application Load Balancer.
What should I do if I get this SAA-C03 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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