Here's another fake Instant Messaging application from the creator of the fake Google Talk program currently in circulation. This time round, the victim is MSN Messenger:

Clicking the "Sign In" button opens up a smaller popup - asking you to fill in your .NET Passport details. Of course, filling in your details will result in a fake "Service could not be found message". Once you leave the PC, the attacker happily wanders over, browses to the C Directory and steals your login details.

These programs seem to be flavour of the month at the moment...