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# ModSecurity Web Application Firewall

ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx that is developed by Trustwave's SpiderLabs. It has a robust event-based programming language which provides protection from a range of attacks against web applications and allows for HTTP traffic monitoring, logging and real-time analysis - https://www.modsecurity.org

The ModSecurity-nginx connector is the connection point between NGINX and libmodsecurity (ModSecurity v3).

The default ModSecurity configuration file is located in `/etc/nginx/modsecurity/modsecurity.conf`. This is the only file located in this directory and contains the default recommended configuration. Using a volume we can replace this file with the desired configuration. To enable the ModSecurity feature we need to specify `enable-modsecurity: "true"` in the configuration configmap.

> Note: the default configuration use detection only, because that minimizes the chances of post-installation disruption. Due to the value of the setting SecAuditLogType=Concurrent the ModSecurity log is stored in multiple files inside the directory `/var/log/audit`. The default `Serial` value in SecAuditLogType can impact performance.

The OWASP ModSecurity Core Rule Set (CRS) is a set of generic attack detection rules for use with ModSecurity or compatible web application firewalls. The CRS aims to protect web applications from a wide range of attacks, including the OWASP Top Ten, with a minimum of false alerts. The directory `/etc/nginx/owasp-modsecurity-crs` contains the owasp-modsecurity-crs repository. Using `enable-owasp-modsecurity-crs: "true"` we enable the use of the rules.