[1] It was written by Ralf Burger in 1986 as a demonstration program for the Chaos Computer Club conference.
[2] In December 1986, Burger distributed the virus at the Chaos Computer Club conference in Hamburg, Germany.
[failed verification][4] Virdem overwrites the host with its own code and saves the original program at the very end.
[failed verification] It infected only files that had a COM extension.
It doesn't intercept interrupt 24h so a write-protected disk gives an "Abort, Retry, Ignore" message.