Inside a Web Application Firewall: How WAFs Actually Inspect HTTP Traffic

A practical look at how Web Application Firewalls analyze HTTP requests, detect attacks, and fit into modern DevOps infrastructure. A Web Application Firewall (WAF) protects web applications by inspecting HTTP requests at the application layer . Unlike traditional firewalls, it analyzes: URLs Query parameters Headers Cookies Request bodies File uploads WAFs detect attacks like: SQL Injection Cross-Site Scripting (XSS) Command Injection File Upload Exploits Application-layer DDoS But they work best when combined with secure coding practices and proper DevOps observability . Why WAF Still Matters in Modern Infrastructure If your API or web service is public, it is already being scanned. Typical traffic hitting public endpoints often looks like this: GET /phpmyadmin GET /.env GET /wp-login.php GET /admin GET /api/users?id=1 OR 1=1 These requests are usually automated vulnerability scans . A WAF acts as a filter between the internet and your application . Typical deployment architecture: I