Back to Glossary

Glossary Term

Web Application Firewall (WAF)

An application-layer firewall that inspects HTTP traffic to block malicious requests targeting web apps.

1 min read

Share this definition

Post it to your feed or send it to teammates.

What it is

A Web Application Firewall (WAF) acts as a protective layer between a web application and the internet. It analyzes incoming HTTP and HTTPS requests to detect and block malicious patterns such as SQL injection, cross-site scripting, or file inclusion attacks.

Unlike network firewalls that focus on IP addresses and ports, WAFs operate at the application layer (Layer 7). They can enforce policies for specific URLs, parameters, or cookies, and can integrate with content delivery networks for distributed protection.

Why it matters

WAFs are essential for defending web-facing applications against automated and manual exploitation attempts. They also help organizations comply with standards like PCI DSS, which mandate application-layer protection for systems handling payment data.

How to reduce risk

  • Use a managed WAF service to keep rules up to date.
  • Customize policies to your application�s specific endpoints.
  • Combine WAF with vulnerability scanning for continuous protection.
  • Log and analyze blocked traffic to refine rules.
  • Avoid over-restrictive settings that break legitimate functionality.