The Microsoft worm was one of Microsoft's more infamous offerings, but little was known of it until it went awry. The worm was implanted into an early version of Microsoft Word as a copy protection scheme. It ran every so often, checking to see if it was a validly licensed copy of Word. If so, the worm went back to sleep, until it woke to check again. If not, the screen went blank, and this message appeared:
The seeds of crime bear bitter fruit!
whereupon the user's data was thoroughly trashed.
Naturally, one day,the worm woke up, trashed an innocent user's data, and caused much outcry among the users of Word. Microsoft denied that this worm ever existed, and was the work of a summer intern. However, this event marked the decline of copy protection schemes in general.
Source: Steal This Computer Book 2