History

A program called “Elk Cloner” is credited with being the first computer virus to appear “in the wild” — that is, outside the single computer or lab where it was created. Written in 1982 by Rich Skrenta, it attached itself to the Apple DOS 3.3 operating system and spread by floppy disk.

Before computer networks became widespread, most viruses spread on removable media, particularly floppy disks. In the early days of personal computers, many users regularly exchanged information and programs on floppies. Some viruses spread by infecting programs stored on these disks, while others installed themselves into the disk boot sector, ensuring that they would be run when the user booted the computer from the disk.

As bulletin board systems and online software exchange became popular in the late 1980s and early 1990s, more viruses were written to infect popularly traded software. Shareware and bootleg software were equally common vectors for viruses on BBSes. Within the “pirate scene” of hobbyists trading illicit copies of commercial software, traders in a hurry to obtain the latest applications and games were easy targets for viruses.

Since the mid-1990s, macro viruses have become common. Most of these viruses are written in the scripting languages for Microsoft programs such as Word and Outlook. These viruses spread in the Microsoft Windows monoculture by infecting documents and sending infected e-mail. Some versions of Word have had bugs in the calls by which macros replicate themselves, causing occasional replication errors, which has sometimes resulted in actual evolution by natural selection. Also, again closely analogous to biological viruses, sometimes when a system gets infected with two Word macro viruses at the same time, recombination can produce a new virus (much as an animal host infected with multiple strains of influenza can produce a novel strain of influenza). There is also the case in which a user gets a computer virus through instant messaging; this process is done by taking the virus code and placing it into a web site’s shortcut which is accessible through Instant Messaging someone. The receiver gets the virus and within a few hours of being on the virus has the capability of transferring itself all the way to the computer’s network.

Add comment September 12th, 2005