Quick Answer
The answer is AWS WAF. This is the correct choice because AWS WAF is a web application firewall specifically designed to inspect HTTP and HTTPS requests at the application layer, allowing it to block common web exploits like SQL injection and cross-site scripting (XSS) before they reach your Application Load Balancer. It integrates directly with an ALB, enabling you to define customizable rules that filter malicious traffic based on request patterns, IP addresses, or URI strings. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this question tests your understanding of how to layer security at the network edge—a common scenario where candidates might mistakenly choose AWS Shield (which protects against DDoS, not application-layer exploits) or a Network ACL (which operates at the transport layer). A helpful memory tip: think of WAF as the “web-aware” filter that reads the content of requests, while Shield is the “shield” against volumetric attacks.
This ANS-C01 practice question tests your understanding of network design. 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 is deploying a web application on Amazon EC2 instances behind an Application Load Balancer (ALB). The ALB is internet-facing and receives traffic from clients. The company wants to improve security by adding an additional layer of protection against common web exploits like SQL injection and cross-site scripting. Which AWS service should they use?
AWS Firewall Manager
Why wrong: Central management of firewall rules.
AWS WAF
Web application firewall that filters SQL injection and XSS.
AWS Shield Advanced
Why wrong: DDoS protection service.
Network ACLs
Why wrong: Stateless packet filtering at subnet level.
Answer choices
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 (Web Application Firewall) is the correct service because it is specifically designed to protect web applications from common exploits such as SQL injection and cross-site scripting (XSS). It integrates directly with an Application Load Balancer (ALB) to inspect HTTP/HTTPS requests and apply customizable rules to block malicious traffic before it reaches the EC2 instances.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
AWS Firewall Manager
Why it's wrong here
Central management of firewall rules.
AWS WAF
Why this is correct
Web application firewall that filters SQL injection and XSS.
Related concept
Read the scenario before looking for a memorised answer.
AWS Shield Advanced
Why it's wrong here
DDoS protection service.
Network ACLs
Why it's wrong here
Stateless packet filtering at subnet level.
Common exam traps
The trap here is that candidates often confuse AWS WAF with AWS Shield Advanced, mistakenly thinking Shield Advanced covers application-layer exploits, when in fact Shield Advanced focuses on volumetric DDoS protection and WAF handles Layer 7 threats like SQL injection and XSS.
Detailed technical explanation
AWS WAF uses a set of rules defined in web access control lists (ACLs) that can match conditions such as SQL-like patterns in the URI query string or body, or script tags in headers. Under the hood, the ALB forwards HTTP/HTTPS requests to the WAF service for inspection before routing traffic to the target group, allowing WAF to block, count, or allow requests based on rule actions. A real-world scenario is a retail site where WAF blocks a request containing '1=1' in a login form parameter, preventing a SQL injection attempt that could expose customer data.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
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FAQ
Network Design — This question tests Network Design — Read the scenario before looking for a memorised answer..
The correct answer is: AWS WAF — AWS WAF (Web Application Firewall) is the correct service because it is specifically designed to protect web applications from common exploits such as SQL injection and cross-site scripting (XSS). It integrates directly with an Application Load Balancer (ALB) to inspect HTTP/HTTPS requests and apply customizable rules to block malicious traffic before it reaches the EC2 instances.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
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. An e-commerce company runs a web application on Amazon EC2 instances in an Auto Scaling group behind an Application Load Balancer. During a flash sale, the application experiences high latency. The network team notices that the ALB is receiving more traffic than expected. What is the most likely cause?
mediumWhy D: Option D is correct because the sudden spike in traffic reaching the ALB beyond expected levels, combined with high latency, strongly indicates that the ALB is being overwhelmed by malicious or excessive traffic. Without AWS WAF protection, the ALB cannot filter out DDoS attacks or unwanted requests at Layer 7, so all traffic passes through to the backend instances, causing resource exhaustion and latency. AWS WAF integrates directly with ALBs to inspect and block malicious traffic before it reaches the application.
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Last reviewed: Jun 24, 2026
This ANS-C01 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 ANS-C01 exam.
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