What is Web Application Firewall (WAF)?

A web application firewall (WAF) is a specific type of application firewall that filters, monitors, and blocks HTTP traffic to and from a specified web service. A WAF sits between external users and web applications and plays a crucial role in securing business-critical web applications and web servers from application-layer attacks. WAFs are different from network firewalls, which provide a barrier between external and internal network traffic, and are therefore designed to protect a secured local-area network (LAN) from unauthorized access.