finger

Internet  utility for locating people on Internet sites . Returns such information as whether a user is logged in, where someone has an account, etc. Many site administrators don't allow Finger requests, because it can help hackers  to break into their server  .

An Internet protocol used to find out more information about an Internet user. (See also Cookies)

Internet service that provides information about the users on a particular computer.

A program that displays information about a particular user, or all users, logged on the local system or on a remote system. It typically shows full name, last login time, idle time, terminal line, and terminal location (where applicable). It may also display plan and project files left by the user.

A program used to find out if someone is online -- it may also reveal their full name and their plan and project files.