The general consensus is that there are none.

Hardware is a common cause of data problems. Power can fail, electronics age, add-in boards can be installed wrong, you can mistype, there are accidents of all kinds, a repair technician can actually cause problems, and magnets you don't know are there can damage disks.

While serious if you have one, viruses are only one way your data can be damaged. You must be prepared for all threats; many of which are more likely to strike than viruses.

A virus reproduces, usually without your permission or knowledge. In general terms they have an infection phase where they reproduce widely and an attack phase where they do whatever damage they are programmed to do (if any). There are a large number of virus types.

A logic bomb will lie dormant until triggered by some event.

There were over 50,000 computer viruses in 2000 and that number was then and still is growing rapidly. Sophos, in a print ad in June 2005 claims "over 103,000 viruses." And, Symantec, in April 2008 is reported to have claimed the number is over one million. Fortunately, only a small percentage of these are circulating widely.

Software interactions are a significant source of problems; but these are inadvertent. Software attacks are deliberate and can also be significant.

Like the horse, a Trojan program is a delivery vehicle; a program that does something undocumented and often malicious.

Virus writers have to balance how and when their viruses infect against the possibility of being detected. Therefore, the spread of an infection may not be immediate.

A dropper is a program that, when run will attempt to install a regular virus onto your hard disk.