Simple virus for teaching

A Slashdot discussion in response to


Currently I am teaching a 101 class on computers. It is more of a ‘demystifying the black box’ type of class. The current topic is computer viruses; I am looking for a virus with which I can infect the lab computers (only connected to local network, no outside network connection) that would be easy for the students to remove by hand. Can the Slashdot community point me in any directions? Is there an executable out there that would work, or do I try to write one myself, or is there one that is written that I can compile myself?”