LaBrea takes over unused IP addresses, and creates virtual servers that are attractive to worms, hackers, and other denizens of the Internet.
The program answers connection attempts in such a way that the machine at the other end gets "stuck", sometimes for a very long time.
Another from Robert Waldner:
Why? Because I see it as a service to the 'net as a whole to tarpit all those worms etc.
More information on this package can be found on the Debian web site.
(If there is a package you would like to see featured here, go to the userinfo page and follow the directions there to submit your entry.)
Now available in RSS and ATOM flavors too.