- A
AWS Shield Standard
Why wrong: AWS Shield Standard provides always-on protection against common DDoS attacks at the network and transport layer, but it does not inspect application-layer content like SQL injection payloads. It cannot block or filter specific HTTP requests.
- B
AWS WAF
AWS WAF is a web application firewall that inspects HTTP and HTTPS requests and can block common threats such as SQL injection and cross-site scripting. It integrates directly with Application Load Balancers, Amazon CloudFront, and API Gateway, making it the correct service for this use case.
- C
Network ACLs
Why wrong: Network ACLs are stateless firewalls that control traffic at the subnet level based on IP addresses, ports, and protocols. They cannot inspect the contents of HTTP requests or block application-layer attacks like SQL injection.
- D
Amazon GuardDuty
Why wrong: Amazon GuardDuty is a threat detection service that continuously monitors for malicious activity and unauthorized behavior using machine learning and threat intelligence. It can detect SQL injection attempts in logs, but it does not actively block the requests; it only generates alerts.
CLF-C02 Security and Compliance Practice Question
This CLF-C02 practice question tests your understanding of security and compliance. 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 runs a public-facing e-commerce website on Amazon EC2 instances behind an Application Load Balancer (ALB). The security team has discovered that attackers are attempting SQL injection attacks through the website's search feature. The company wants to use a managed AWS service to inspect incoming HTTP requests and block these malicious payloads before they reach the application. Which AWS service should the company use?
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
AWS WAF
AWS WAF is a managed web application firewall that allows you to create rules to inspect HTTP/HTTPS requests and block common attack patterns, such as SQL injection and cross-site scripting. By associating a WAF web ACL with the Application Load Balancer, the company can filter incoming traffic and block malicious payloads before they reach the EC2 instances.
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.
- ✗
AWS Shield Standard
Why it's wrong here
AWS Shield Standard provides always-on protection against common DDoS attacks at the network and transport layer, but it does not inspect application-layer content like SQL injection payloads. It cannot block or filter specific HTTP requests.
When this WOULD be correct
A company wants to protect its EC2 instances from common DDoS attacks (e.g., SYN floods, UDP reflection) at no additional cost. AWS Shield Standard is automatically enabled and would be the correct answer.
- ✓
AWS WAF
Why this is correct
AWS WAF is a web application firewall that inspects HTTP and HTTPS requests and can block common threats such as SQL injection and cross-site scripting. It integrates directly with Application Load Balancers, Amazon CloudFront, and API Gateway, making it the correct service for this use case.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Network ACLs
Why it's wrong here
Network ACLs are stateless firewalls that control traffic at the subnet level based on IP addresses, ports, and protocols. They cannot inspect the contents of HTTP requests or block application-layer attacks like SQL injection.
When this WOULD be correct
A company needs to block traffic from a specific IP range at the subnet boundary to reduce load on the application layer. Network ACLs would be the correct choice because they provide stateless filtering at the VPC subnet level.
- ✗
Amazon GuardDuty
Why it's wrong here
Amazon GuardDuty is a threat detection service that continuously monitors for malicious activity and unauthorized behavior using machine learning and threat intelligence. It can detect SQL injection attempts in logs, but it does not actively block the requests; it only generates alerts.
When this WOULD be correct
A company wants to detect potential security threats across AWS accounts and workloads by analyzing VPC Flow Logs, DNS logs, and CloudTrail events, and receive alerts about suspicious activity such as compromised instances or reconnaissance attempts.
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 CLF-C02 exam frequently reuses these exact scenarios with slightly different constraints.
✓AWS WAFCorrect answer▾
Why this is correct
AWS WAF is a web application firewall that inspects HTTP and HTTPS requests and can block common threats such as SQL injection and cross-site scripting. It integrates directly with Application Load Balancers, Amazon CloudFront, and API Gateway, making it the correct service for this use case.
✗AWS Shield StandardWrong answer — click to see why▾
Why this is wrong here
AWS Shield Standard provides DDoS protection but does not inspect application-layer payloads like SQL injection strings; it only mitigates volumetric attacks.
★ When this WOULD be the correct answer
A company wants to protect its EC2 instances from common DDoS attacks (e.g., SYN floods, UDP reflection) at no additional cost. AWS Shield Standard is automatically enabled and would be the correct answer.
Why candidates choose this
Candidates may confuse 'security' broadly with 'attack protection' and assume Shield covers all attack types, including application-layer threats like SQL injection.
✗Network ACLsWrong answer — click to see why▾
Why this is wrong here
Network ACLs are stateless and operate at the subnet level, filtering traffic based on IP addresses, ports, and protocols. They cannot inspect application-layer payloads like SQL injection attempts.
★ When this WOULD be the correct answer
A company needs to block traffic from a specific IP range at the subnet boundary to reduce load on the application layer. Network ACLs would be the correct choice because they provide stateless filtering at the VPC subnet level.
Why candidates choose this
Candidates may confuse network-layer filtering with application-layer inspection, assuming that any security control at the network perimeter can block SQL injection attacks.
✗Amazon GuardDutyWrong answer — click to see why▾
Why this is wrong here
Amazon GuardDuty is a threat detection service that monitors for malicious activity and unauthorized behavior, but it does not actively inspect and block HTTP requests at the application layer like a web application firewall. It cannot prevent SQL injection attacks in real-time.
★ When this WOULD be the correct answer
A company wants to detect potential security threats across AWS accounts and workloads by analyzing VPC Flow Logs, DNS logs, and CloudTrail events, and receive alerts about suspicious activity such as compromised instances or reconnaissance attempts.
Why candidates choose this
Candidates may confuse GuardDuty's threat detection capabilities with active request filtering, assuming it can block attacks because it identifies malicious patterns, but it is a detection-only service without inline prevention.
Analysis generated from the official CLF-C02blueprint 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 confuse AWS Shield (which protects against DDoS at Layer 3/4) with AWS WAF (which protects against application-layer attacks like SQL injection), leading them to choose Shield Standard instead of WAF.
Detailed technical explanation
How to think about this question
AWS WAF uses customizable rules that can match against request components such as URI, query string, headers, and body using pattern-matching or SQL injection match conditions. Under the hood, WAF integrates with ALB via a web ACL association, and the ALB passes the request to WAF for inspection before forwarding it to the target group. A real-world scenario where this matters is when attackers encode SQL injection payloads (e.g., using URL encoding or nested comments) to bypass simple string matching; WAF's SQL injection match condition can decode and detect these obfuscated patterns.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
Visual reference
What to study next
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FAQ
Questions learners often ask
What does this CLF-C02 question test?
Security and Compliance — This question tests Security and Compliance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: AWS WAF — AWS WAF is a managed web application firewall that allows you to create rules to inspect HTTP/HTTPS requests and block common attack patterns, such as SQL injection and cross-site scripting. By associating a WAF web ACL with the Application Load Balancer, the company can filter incoming traffic and block malicious payloads before they reach the EC2 instances.
What should I do if I get this CLF-C02 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
This CLF-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CLF-C02 exam.
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