ModSecurity is an open-source rule-based Web Application Firewall (WAF) that runs directly inside your web server. You can install it as a module for Apache, Nginx, or IIS. It analyzes incoming traffic, applies security rules, and helps block malicious requests before they reach your application. It provides an additional protection layer without requiring changes to your code.
Frequently Asked Questions
Find answers to the most commonly asked questions about ModSecurity. If you can’t find what you’re looking for, please don’t hesitate to reach out to our team directly.
No, ModSecurity is not end of life. The project’s custodianship moved from Trustwave to OWASP, where it now continues under open governance. Development is guided by a transparent leadership model and an active community committed to maintaining and improving ModSecurity.
ModSecurity is now maintained by OWASP, supported by a wider community of contributors. Instead of a single vendor, the project is developed collaboratively by volunteers, security specialists, and organizations that actively improve the codebase and rule sets.
No. ModSecurity is not a standalone WAF. It works as a module inside a web server such as Apache, Nginx, or IIS, and relies on that server to process traffic. Instead of running as a separate appliance or proxy, it adds WAF capabilities directly into your existing server environment.
ModSecurity supports all major server environments. It can run on Linux, Unix-like systems, Windows, and macOS when paired with a compatible web server. Its modules integrate with Apache, Nginx, and IIS, making it suitable for most hosting setups and deployment workflows.
No, you don’t need the OWASP Core Rule Set to use ModSecurity. ModSecurity can run on its own. That said, the Core Rule Set adds a well-tested collection of security rules that greatly strengthens the overall protection. Most users enable CRS because it offers immediate, broad coverage against common web attacks with minimal setup.
Yes, ModSecurity can block attacks automatically. When it’s running in blocking mode, it can stop requests that match your security rules. Most users pair it with the OWASP Core Rule Set for automatic detection and blocking of common web attacks.
You can install ModSecurity by following the official setup instructions for your specific web server. The full installation guide is available at modsecurity.org/installation.
Yes, ModSecurity can have a small impact on performance because it inspects every incoming request. In most real-world environments, this overhead is minimal, and proper tuning — like enabling only the rules you actually need — helps the site run smoothly.
The key difference is that ModSecurity is the Web Application Firewall (WAF) engine, while the OWASP Core Rule Set (CRS) is a collection of rules that runs on top of it. ModSecurity handles request inspection and enforcement, and CRS provides patterns for detecting common web attacks. You can use ModSecurity with CRS or with other custom or third-party rule sets, depending on your needs.
The essential configuration guidance is included in the Configuration section of the Installation Guide.
Yes, we welcome sponsorships. If you’d like to support the project, please feel free to send us an email.