Know the Common Viruses

Which are the most common viruses? We've answered this question several times. Each time, we have produced slightly different answers because the specific numbers reported depend on how precisely the virus is defined in the survey, the actual rates of infection in the locality surveyed, and the reporting rate. (It is likely that Michelangelo infections have been reported at higher rates relative to their incidence frequency than has Jerusalem.Standard). Our current answer is a result of compiling information from several sources: market research, our own tallies, and tallies from virus researchers around the world.

The table below lists and describes the 10 most common viruses.

Virus Name | Comment
Cascade.1701 | Often identified merely as Cascade, this 1987 Swiss virus may cause the text on your CGA screen to fall to the bottom line. The original caused this cascading effect in October, November, or December of 1988 only variations may not display the effect at all. This family adds 1701 bytes to COM files, not infecting EXE files. The virus is encrypted beyond the first 35 bytes.
Cascade.1704 | Often identified merely as Cascade, from which it was derived. Adds 1704 bytes to files, may cause random reboots, and won't drop any letters from your screen.
Dark Avenger.1 | Often identified merely as Dark Avenger. Written by a Bulgarian who calls himself Dark Avenger and called this, his (and Bulgaria's) first virus Eddie version 1.0". Written in September, 1988, it adds 1800 bytes to COM and EXE files. Contains no text, does no damage, infects well.
Dark Avenger.4 | Often identified as Dark Avenger, Eddie II, V2100, and 2100. This variant is 2100 bytes.
Frodo | Often identified as 4096 or 4K (for the number of bytes it adds), 100 years (because it marks files as infected by adding 100 years to the file's date stamp, Frodo (because it tries to place a boot sector birthday message to Frodo in the fall) or Stealth (because once in memory, its size increase does not show with the DIR command.) Infects COM and EXE files rapidly, including COMMAND.COM, and infects on file open, so if it isn't detected by your scanner when it is in memory, it will infect every file your scanner opens to check.
Green Caterpillar.1 | Often identified as 1575 and/or 1591, this virus is spreading rapidly, despite the fact that it lets DOS place the date/time on the file showing when it became infected. Infects COM and EXE files, adding 1575 bytes (or so). Infects when a DIR or COPY command is executed, rather than when files are executed. Likely to make your screen lurch when you give a DIR command, as it pauses to infect something. May display a green caterpillar.
Jerusalem.Standard | Often identified as Jerusalem or Jerusalem-B, this October 1987 virus infects COM and EXE files, adding 1813 bytes to the size of COM files and re-infecting EXE files. Memory resident, it infects files as they are run. The original deleted the file you were executing on Friday 13th, but numerous variants now perform this miracle on a variety of date conditions. One half hour after going memory resident, the original scrolls up a bit of your screen, revealing a black hole, one of its synonyms.
Michelangelo | Recent star of stage and screen, Michelangelo is derived from Stoned.Standard. Infecting only 5.25" disks in drive A: and the Master Boot Record of C:, it does nothing but spread well until March 6. On March 6, booting with this boot virus will give it a chance to overwrite your entire boot drive, starting from the outside tracks. Predictions of 5 million infections were untrue. This virus appeared in June, 1991, barely makes our Top Ten chart, and is very rare.
Stoned.Standard | Often identified as Stoned, this was written by a 16 year old in New Zealand in 1988, rapidly spreading worldwide. The original only infected 360K disks in drive A: and the Master Boot Record of C:. Intended to cause no damage, it overwrites a sector of the FAT on hard disks lacking slack space, and variants willingly cause damage to root or FAT on 3.5" floppies. The original displayed the message Your PC is now Stoned! in one of 8 or so boots from an infected floppy. The boot sector will contain the non-displaying message Legalise Marijuana! in the original.
Yankee Doodle 2885 | Often identified as TP44VIR, this is the 44th version of a virus series written by a Bulgarian author with the initials T.P. in September, 1989. It plays Yankee Doodle at 5PM, but causes no damage.