What's the designed purpose of modsecurity for Apache/Nginx?
Does it play the role of authentication (Basic/Forms/Cookie)?
From my research, it appears to be a Web Application Firewall feature. The features like Authentication are best left to the native web-server authentication functionality like mod_auth_basic or the application framework security components.
Researched Sources
ModSecurity is a web application firewall (WAF). It is not used for authentication.
ModSecurity™is an open source, free web application firewall (WAF) Apache module. - - WAFs are deployed to establish an external security layer that increases security, detects and prevents attacks before they reach web applications. It provides protection from a range of attacks against web applications and allows for HTTP traffic monitoring and real-time analysis with little or no changes to existing infrastructure.
The FAQ on What type(s) of security models does ModSecurity support? lists four security models: Negative Security Model, Positive Security Model, Virtual Patching & Extrusion Detection Model.
