Ibex aka Bones replicates when you boot from an infected floppy. Once you infect a machine, all accessed floppies get the virus.

Ibex has code to activate and overwrite all of the hard drive on the 7th of each month when any floppy disk is accessed.

Ibex was reported to be in the wild in USA in December 1995.

[Analysis: Mikko Hypponen, F-Secure]