That, of course is the best case scenario. This once again proves that the most valuable thing on your desktop is your data . Last year, it was estimated that the CIH virus damaged several hundred thousand computers. That was due, in part, to a large unprotected area of the world map, and to wide infestation of the virus in the wild. But field detection rates of CIH are at an all time high even now, two years after the virus was first reported in the wild.
Viruses enter the wild, and circulate, by a various methods.
The biggest driving factor is the nature of the virus in question. Since CIH is not an email worm, or a macro virus, but a PE virus, it only circulates on an infected computer program. Two different vectors have moved it out into a durable circulation cycle. The first, and most unusual is that a major manufacturer was infected on its assembly line and distributed many infected new computers. This method of infection is not unique, but is usually attributed to software companies, not hardware.