Computer program that modifies other programs to replicate itself and spread
Hex dump of the Brain virus, generally regarded as the first computer virus for the IBM Personal Computer (IBM PC) and compatibles
A computer virus[1] is a type of malware that, when executed, replicates itself by modifying other computer programs and inserting its own code into those programs.[2][3] If this replication succeeds, the affected areas are then said to be "infected" with a computer virus, a metaphor derived from biological viruses.[4]
Computer viruses generally require a host program.[5] The virus writes its own code into the host program. When the program runs, the written virus program is executed first, causing infection and damage. By contrast, a computer worm does not need a host program, as it is an independent program or code chunk. Therefore, it is not restricted by the host program, but can run independently and actively carry out attacks.[6][7]
As of 2013, computer viruses caused billions of dollars' worth of economic damage each year.[10] In response, an industry of antivirus software has cropped up, selling or freely distributing virus protection to users of various operating systems.[11]
Ludwig, Mark A. (1996). The Little Black Book of Computer Viruses: Volume 1, The Basic Technologies. American Eagle Publications. pp. 16–17. ISBN0-929408-02-0.