| A computer virus is a self-replicating | | | | programs, and viruses were written to infect |
| computer program written to alter the way a | | | | popularly traded software. Shareware and |
| computer operates, without the permission or | | | | bootleg software were equally common vectors |
| knowledge of the user. | | | | for viruses on BBS's. |
| | | | |
| Elk Cloner is credited with being the first | | | | Since the mid-1990s, macro viruses have |
| computer virus to appear "in the wild" -- | | | | become common. Most of these viruses are |
| outside the single computer or lab where it | | | | written in the scripting languages for |
| was created. Written in 1982 by Rich Skrenta, | | | | Microsoft programs such as Word and Excel. |
| it attached itself to the Apple DOS 3.3 | | | | These viruses spread in Microsoft Office by |
| operating system and spread by floppy disk. | | | | infecting documents and spreadsheets. Since |
| The first PC virus was a boot sector virus | | | | Word and Excel were also available for Mac |
| called (c)Brain, created in 1986 by two | | | | OS, most of these viruses were able to spread |
| brothers, Basit and Amjad Farooq Alvi, | | | | on Macintosh computers as well. |
| Pakistan. The brothers reportedly created the | | | | |
| virus to deter pirated copies of software | | | | A computer virus may also be transmitted |
| they had written. | | | | through instant messaging. A virus may send a |
| | | | web address link as an instant message to all |
| Before computer networks became widespread, | | | | the contacts on an infected machine. If the |
| most viruses spread on removable media, | | | | recipient, thinking the link is from a friend |
| particularly floppy disks. In the early days | | | | (a trusted source) and follows the link to |
| of the personal computer, many users | | | | the website, the virus hosted at the site may |
| regularly exchanged information and programs | | | | be able to infect this new computer and |
| on floppies. Some viruses spread by infecting | | | | continue propagating. |
| programs stored on these disks, while others | | | | |
| installed themselves into the disk boot | | | | The newest species of the virus family is the |
| sector. | | | | cross-site scripting virus. The virus emerged |
| | | | from research and was academically |
| Traditional computer viruses emerged in the | | | | demonstrated in 2005. This virus utilizes |
| 1980s, driven by the spread of personal | | | | cross-site scripting vulnerabilities to |
| computers and the resultant increase in BBS | | | | propagate. Since 2005 there have been |
| and modem use, and software sharing. Bulletin | | | | multiple instances of the cross-site |
| board driven software sharing contributed | | | | scripting viruses in the wild, most notable |
| directly to the spread of Trojan horse | | | | sites affected have been MySpace and Yahoo. |