Web Application Firewall

This is a countermeasure. To view all countermeasures, please see the Countermeasure Category page.

Description

A web application firewall (WAF) is an appliance, server plugin, or filter that applies a set of rules to an HTTP conversation. Generally, these rules cover common attacks such as cross-site scripting (XSS) and SQL injection. By customizing the rules to your application, many attacks can be identified and blocked. The effort to perform this customization can be significant and needs to be maintained as the application is modified.

A far more detailed description is available at Wikipedia.

Important selection criteria

For more information on web application firewall evaluation criteria, please visit Web Application Firewall Evaluation Criteria.

Tools

OWASP tools of this type

• The OWASP Stinger Project is not a full blown WAF, but it is a strong Java/J2EE input validation filter that can be put in front of your application.
• NAXSI is a WAF for NGINX.

Well-known open source tools of this type

• AQTronix - WebKnight
• Trustwave SpiderLabs - ModSecurity
• Qualys - Ironbee (A recent new project by Qualys led by Ivan Ristic, the original ModSecurity author)
• QuickDefence-WAF (Nginx and Lua based first open source WAF, still in pre-alpha stage)