Password Sharing Protection - What Script Are You Using?

We use a proprietary script that we had coded to handle this from a two pronged approach, IP and Username.

We block users that use the same username from the same class C range of the IP within 24 hour period, with an adjustable threshold
level of sensitivity. Using the Class C range of the IP allows for multiple dial ins by AOL users or other ISP users that have dynamic IP assignment per dialup.

When it is flagged first, it removes it for one hour, then gives it a second chance. If it happens again after that in a 24 hour period, it blocks it and sends us a notice email.

We then change the password and send out a nice little email to the
registered user.