Professionals in the field of
security sometimes use the term landmine to refer to a
trojan horse that is deliberately installed on a system as a
countermeasure to hackers who successfully penetrate their system.
Here's an example of a landmine:
A hacker successfully roots your Linux system. He types in a standard command like "ps ax". Unknown to the hacker, you have installed a landmine named "ps" that will perform the standard "ps" function plus the added step of paging all administrators as well as running a script that will turn off all network services. The hacker believes he only checked the currently running processes, but what he really did was trip over a trojan horse that you the administrator installed.
Landmines complement a system complete with honeypots, intrusion detection systems, other forms of trickery, and your standard security precautions.