A Web Application Firewall (WAF) helps protect web applications by filtering and monitoring HTTP traffic between a web application and the Internet. It typically protects web applications from attacks such as cross-site forgery, cross-site-scripting (XSS), file inclusion, and SQL injection, among others.
A WAF provides a layer of defense against common application vulnerabilities (OWASP Top 10). It can block malicious traffic patterns before they reach the application servers, buying time for teams to patch underlying code vulnerabilities.
A WAF is a necessary hygiene factor, but not a complete solution. We deploy WAFs at the edge (Layer 7) but operate under the assumption that they can be bypassed. True security comes from secure coding practices, input validation, and parameterized queries, not just filtering rules.