Web Application Firewall (WAF)

A Web Application Firewall (WAF) sits in front of a web application — usually as a reverse proxy, sidecar, or CDN edge service — and analyses each HTTP request and response against rule sets such as the OWASP Core Rule Set. It can block injection attempts, malicious file uploads, scanner traffic, layer-7 DDoS, credential stuffing, and bot abuse, often using a mix of signatures, anomaly scoring, rate limiting, and machine-learning models. WAFs are essential for protecting legacy or third-party apps that cannot be patched quickly. They must be tuned to reduce false positives, run in detection mode before blocking, and be combined with secure coding rather than treated as a substitute for it.