This is a port of the MacBill, which is based on xbill, source to GNUstep.

Ever get the feeling that nothing is going right?  You're a sysadmin, and
someone's trying to destroy your computers.  The little people running
around the screen are trying to infect your computers with Wingdows [TM],
a virus cleverly designed to resemble a popular operating system.  Your
objective is to click the mouse on them, ending their potential threat.
If one of the people reaches a computer, it will attempt to replace your
operating system with the virus it carries. It will then attempt to run off
the screen with your vital software.

LICENSE: GPL2 or later

WWW: http://gnu.ethz.ch/linuks.mine.nu/stepbill/