PAM - Pluggable Authentication Modules

An introduction to PAM by Kurt Seifried. PAM (Pluggable Authentication Modules) provides the backbone of most authentication in modern Linux systems (and can be implemented in others, such as Solaris), yet it is typically ignored and woefully under-utilized. Anytime you log into a modern Linux system, whether via telnet, ssh, pop, ftp, and so on, you are using PAM to process the authentication request.