PAM stands for Pluggable Authentication Modules. These are authentication modules for services, such as LDAP or Radius, that can be 'plugged' into the authentication process on a Linux or Sun Solaris host. This functionality provides the ability to custom how and by what mechanism that users, applications and processes are authorized.
For example, if you wished to enable two-factor authentication for your Linux system, then a PAM module might achieve this for you.
This was first published in July 2006