In 1991, in Australia, Roger Riordan from Cybec discovered a new variant of the Stoned virus. The new threat was a boot sector virus, which infected the hard disk’s master boot record and the floppy disk boot sector. When researchers discovered that the virus contained a destructive payload triggering on the 6th of March each year, it gained the name Michelangelo. (The Italian Renaissance artist was born on March 6, 1475.)
Before Michelangelo, viruses were usually discreet and confined to the antivirus-specialist world. In March 1992, however, this virus changed the way the world looked at malware. With this newcomer, viruses really came into the public eye.
In March 1992, antivirus researchers knew of about 1,000 viruses, and payloads in those days frequently used a trigger date. I remember that March 13, 1992, was a Friday; that was the day when Jerusalem activated its payload. Today malware have different goals. When they spread, their payloads are generally not destructive but discreet. Their aim now is to earn money for their designers, and not show up only one day in the year.