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](https://www.modsecurity.org)
The [ModSecurity-nginx](https://github.com/SpiderLabs/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.
Due to the value of the setting [SecAuditLogType=Concurrent](https://github.com/SpiderLabs/ModSecurity/wiki/Reference-Manual-(v2.x)#secauditlogtype) 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 Core Rule Set repository](https://github.com/coreruleset/coreruleset).
