Every month there are more than two hundred new viruses discovered every month. Of these 12,000, only 250 or so are circulating just waiting to be unleashed on another victim. Damages from computer viruses was estimated to be over $1 billion last year and is expected to rise to two to three billion this year.1 .
A computer virus is an executable code that, when run by someone, attaches itself to other executable codes in a computer in an effort to reproduce itself.2 Some computer viruses are very destructive, by deleting files or causing systems to freeze. There are other viruses that are just there to be an annoyance. The number of things a virus can be programmed to do is endless.
Computer viruses do not run by themselves. They require an operating system for activation. Once a virus has been activated, it searches the computer system for other programs to infect. Viruses can only infect executable programs not plain data.
History of Computer Viruses.
In 1948 John Von Neumann showed mathematically that it was possible to build a computer program.3 At that time however, most experts did not take him seriously. A few scientists went on to pursue his ideas. By 1959 a self-replicating program was put into a game created at AT&T's Bell Laboratories.4 In the game, each program tries to destroy each other by overwriting its instructions. At the same time both programs are continuously making copies of themselves. The winner was the one whose programs were most abundant. These programs became the first worms.
This game idea soon spread to other research laboratories and became quite popular over the next two decades. Theses games were usually played under controlled conditions. When networks were established, the capabilities of the game that was created became quite clear. A program that copies itself could devastate a network of connected computers. In a series of experiments by Xerox, a non-malicious worm program demonstrated its ability to propagate rapidly through a network.