The answer is Azure Web Application Firewall (WAF). This service is the correct choice because it provides network filtering at the application layer (Layer 7), inspecting HTTP/HTTPS traffic to detect and block common exploits like SQL injection and cross-site scripting (XSS) using rule sets such as the OWASP Core Rule Set. On the Microsoft Azure Fundamentals AZ-900 exam, this question tests your understanding of how Azure WAF differs from other network security services like Azure Firewall or Network Security Groups—WAF is specifically for web application protection, not general network traffic. A common trap is confusing WAF with Azure Firewall, but remember: WAF focuses on web app exploits at Layer 7, while Azure Firewall handles broader network filtering. Memory tip: think "WAF = Web App Firewall" and associate the "W" with "Web" and "Layer 7" to keep it distinct.
AZ-900 Describe Azure architecture and services Practice Question
This AZ-900 practice question tests your understanding of describe azure architecture and services. 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 Azure service provides network filtering to protect web applications from common exploits like SQL injection and cross-site scripting?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Azure Web Application Firewall (WAF)
Azure Web Application Firewall (WAF) is specifically designed to inspect and filter HTTP/HTTPS traffic at the application layer (Layer 7). It uses rule sets like the OWASP Core Rule Set to detect and block common web exploits such as SQL injection and cross-site scripting (XSS), making it the correct choice for protecting web applications.
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.
✗
Azure Firewall
Why it's wrong here
Azure Firewall is a network-level firewall; WAF specifically targets web application attacks at layer 7.
✗
Azure DDoS Protection
Why it's wrong here
DDoS Protection defends against volumetric attacks; WAF protects web apps from application-layer exploits.
✗
Network Security Groups (NSG)
Why it's wrong here
NSGs filter network traffic at the subnet/NIC level; WAF provides application-layer protection for web apps.
✓
Azure Web Application Firewall (WAF)
Why this is correct
WAF protects web applications from SQL injection, XSS, and other OWASP Top 10 vulnerabilities.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse Azure Firewall (a general network firewall) with Azure WAF (an application-layer firewall), because both have 'firewall' in their name, but they operate at different OSI layers and serve distinct purposes.
Detailed technical explanation
How to think about this question
Azure WAF can be deployed with Azure Application Gateway, Azure Front Door, or Azure Content Delivery Network (CDN). It evaluates each HTTP request against a managed rule set (e.g., OWASP 3.x) that includes regex patterns for common attack signatures, such as detecting 'OR 1=1' patterns for SQL injection or '<script>' tags for XSS. In a real-world scenario, WAF can also be configured with custom rules to block traffic from specific geographies or to allow only certain HTTP methods, providing defense-in-depth for web applications.
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 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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-900 question in full detail.
Describe Azure architecture and services — This question tests Describe Azure architecture and services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Azure Web Application Firewall (WAF) — Azure Web Application Firewall (WAF) is specifically designed to inspect and filter HTTP/HTTPS traffic at the application layer (Layer 7). It uses rule sets like the OWASP Core Rule Set to detect and block common web exploits such as SQL injection and cross-site scripting (XSS), making it the correct choice for protecting web applications.
What should I do if I get this AZ-900 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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Question Discussion
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