SAA-C03 Practice Question: AWS WAF operates at Layer 7 (application layer).
A web application for a healthcare document service is behind an Application Load Balancer. The application must be protected from common SQL injection and cross-site scripting attacks with minimum operational overhead. What should the architect deploy? The design must avoid adding custom operational scripts.
⚠ Common exam trap
It's easy for candidates to confuse network-layer security controls (security groups, network ACLs, or Shield) with application-layer protection, assuming they can block SQL injection or XSS, when in fact only a web application firewall like AWS WAF can inspect and filter HTTP payloads for such attacks.
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 associated with the Application Load Balancer
AWS WAF is a web application firewall that integrates directly with an Application Load Balancer to filter and monitor HTTP/HTTPS requests. It provides managed rules specifically designed to block common attack patterns like SQL injection and cross-site scripting (XSS) without requiring custom scripts or manual rule maintenance, thus meeting the requirement for minimum operational overhead.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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Security groups on the application instances
Why it's wrong here
Security groups are stateful instance-level firewalls permitting or denying traffic by IP, port and protocol; they cannot parse HTTP payloads, so injection and scripting strings reach the application. They would be correct for restricting which sources may reach the instances. AWS WAF inspects layer 7 requests.
- ✓
AWS WAF associated with the Application Load Balancer
Why this is correct
AWS WAF attached to the Application Load Balancer inspects incoming HTTP requests and blocks SQL injection and cross-site scripting using managed rule groups, satisfying the minimum-operational-overhead constraint without custom scripts. Rules are evaluated at the load balancer before traffic reaches the application, providing managed protection with no code changes.
- ✗
Network ACLs on the public subnets
Why it's wrong here
Network ACLs filter at the subnet boundary by IP, port and protocol, so they cannot inspect HTTP request payloads for SQL injection or cross-site scripting patterns. They would be correct for blocking specific source CIDR ranges or ports. AWS WAF on the ALB evaluates layer 7 content against managed rule groups.
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AWS Shield Advanced only
Why it's wrong here
AWS Shield Advanced defends against volumetric and layer 3/4 distributed denial-of-service attacks; it performs no inspection of HTTP request bodies, so SQL injection and XSS payloads pass through. Shield Advanced would be correct if the requirement were DDoS resilience with cost protection. AWS WAF handles layer 7 attack patterns.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SAA-C03 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 SAA-C03 exam.