4.3- Not Stoned Again
Figure 10: The Stoned virus, a boot infector, rose in prevalence and then declined.
The Stoned virus was first observed in an incident in 1989. It is a typical boot virus, infecting diskette boot records and master boot records of hard disks. One time out of eight that a system is booted from an infected diskette, the message ``Your PC is now Stoned!'' will appear on the display. The virus has no other effects. The Stoned virus followed the expected pattern of rising in prevalence through 1991, at which time it had reached a rough equilibrium. After a large peak during Michelangelo Madness, it slowly declined in prevalence over the next several years. Once the most prevalent virus in the world, the Stoned virus is seen much less frequently today. Its rise in prevalence and subsequent equilibration is what we expect of a virus. Its decline is a bit puzzling at first, until we notice that a system infected with the Stoned virus only spreads that infection to the diskette in the A: drive, not to any other diskette drive. The system became infected in the first place by booting from an infected diskette in the A: drive. The Stoned virus started its life on 5.25-inch diskettes. In spreading from diskette to system to diskette, it could only spread to other 5.25-inch diskettes. Early in Stoned's life, most systems used 5.25-inch drives, so there was a fertile medium around the world which Stoned could use to spread. In the late 1980s, however, a trend began towards systems that used 3.5-inch drives as their A: drive. The fraction of systems that had 5.25-inch A: drives declined, and has been declining steadily ever since. With fewer and fewer systems that Stoned could infect and spread between, the virus too declined in prevalence.
|