Finger

This utility, which is available for both UNIX and NT, outputs information about a system's users. If hackers provide a first or last name, the utility returns the logon names of users with matching first or last names. If hackers provide an email address, the utility returns user profile information (e.g., the user's full name) and specifies whether the user is currently logged on. After hackers have a list of usernames, the task of systematically discovering passwords becomes the game. Because of these security problems, avoid using this utility.