The answer is Azure Application Gateway with WAF, which acts as a reverse proxy at Layer 7 to inspect and filter incoming HTTP/HTTPS traffic before it reaches your web servers. This service is correct because it combines load balancing with a Web Application Firewall (WAF) based on the OWASP Core Rule Set, actively blocking common web exploits like SQL injection and cross-site scripting (XSS) at the application layer. On the Microsoft Azure Fundamentals AZ-900 exam, this question tests your understanding of how Azure provides centralized web application security, often appearing alongside other network services like Azure Front Door or Azure Firewall—a common trap is confusing the Layer 7 reverse proxy of Application Gateway with the Layer 3/4 network filtering of Azure Firewall. To remember, think of the gateway as a smart security guard at the entrance of your web app, not just a firewall at the network door. A useful memory tip: "WAF on the Gateway" rhymes with "protect your app today."
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 acts as a reverse proxy with Web Application Firewall (WAF) capabilities to protect web applications from common web exploits?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Azure Application Gateway with WAF
Azure Application Gateway with WAF is the correct choice because it operates as a Layer 7 reverse proxy, inspecting HTTP/HTTPS traffic and using a Web Application Firewall (WAF) to block common exploits such as SQL injection and cross-site scripting (XSS). The WAF is based on the OWASP Core Rule Set (CRS), providing centralized protection for 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 stateful firewall — Application Gateway with WAF provides application-layer (layer-7) web protection.
✓
Azure Application Gateway with WAF
Why this is correct
Application Gateway with WAF provides layer-7 load balancing and protects web apps from OWASP Top 10 vulnerabilities.
Related concept
Read the scenario before looking for a memorised answer.
✗
Network Security Groups
Why it's wrong here
NSGs filter traffic at layers 3/4 based on IP and port — they don't inspect HTTP payloads for web exploits.
✗
Azure DDoS Protection
Why it's wrong here
DDoS Protection mitigates volumetric attacks — WAF protects against application-layer exploits like SQL injection.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse Azure Firewall (a network-layer firewall) with Application Gateway (a Layer 7 reverse proxy), mistakenly thinking any 'firewall' service can provide web application protection, but only Application Gateway with WAF offers dedicated Layer 7 inspection and OWASP-based exploit blocking.
Detailed technical explanation
How to think about this question
Under the hood, Azure Application Gateway terminates SSL/TLS connections and routes traffic based on URL path, host headers, or other HTTP attributes, while the WAF engine inspects each request against the OWASP CRS rulesets (e.g., 3.2) in real time. A subtle behavior is that the WAF can run in detection mode (log only) or prevention mode (block requests), and it supports custom rules for fine-grained control. In a real-world scenario, an e-commerce site might use Application Gateway with WAF to protect its checkout API from SQL injection while also offloading SSL termination and enabling cookie-based session affinity.
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 Application Gateway with WAF — Azure Application Gateway with WAF is the correct choice because it operates as a Layer 7 reverse proxy, inspecting HTTP/HTTPS traffic and using a Web Application Firewall (WAF) to block common exploits such as SQL injection and cross-site scripting (XSS). The WAF is based on the OWASP Core Rule Set (CRS), providing centralized protection for 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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