WAF
Web Application Firewall: filters and monitors HTTP traffic between a web application and the internet. Blocks SQL injection, XSS, and other OWASP top-10 attacks.
What is WAF?
Web Application Firewall: filters and monitors HTTP traffic between a web application and the internet. Blocks SQL injection, XSS, and other OWASP top-10 attacks.
WAF is a intermediate-level concept that sits in the Security Architecture area of system design. Engineers reach for it whenever they need to reason about real-world trade-offs in that space — not just for textbook correctness, but because real production systems at companies like Netflix, Amazon, and Google make these decisions every day.
If you want to go deeper than this definition — with diagrams, code, and a quiz to lock it in — work through the "WAF" lesson linked below. It walks through the why, the mechanism, the trade-offs, and how the giants actually use it in production.
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Full interactive lesson with diagrams, code examples, real-world references, and a quiz.
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See also
Related glossary terms you might want to look up next.
SQL Injection
An attack where malicious SQL is inserted into a query through user input. Prevented by parameterized queries and prepared statements. Never concatenate user input into SQL.
XSS
Cross-Site Scripting: an attack where malicious scripts are injected into trusted websites. Prevented by sanitizing user input and setting Content-Security-Policy headers.
Reverse Proxy
A server that sits in front of your backend servers and forwards client requests to them. Handles SSL termination, caching, and load balancing.