Definition
A web application firewall WAF is a security solution that filters inspects and monitors HTTP traffic between a web application and the internet. It acts as a reverse proxy, sitting in front of web applications to protect them from various application layer attacks. WAFs work by applying a set of rules to incoming requests to identify and block malicious traffic patterns. Implementing a WAF is crucial for safeguarding sensitive data and ensuring the availability of web services by preventing common threats like SQL injection cross site scripting and denial of service attacks. For instance, a WAF can block an incoming request containing suspicious code that attempts to exploit a known vulnerability in a web application's login form. Unlike a traditional network firewall that operates at lower network layers, a WAF focuses specifically on the application layer protocols and threats targeting web applications. This concept is frequently tested on certifications such as CompTIA Security+ CySA+ and CISSP.