There have been so many discussions regarding computer virus's that even a person who knows nothing about computers knows what it is. As portrayed by the media and government, virus's are bad, and indeed they are. Or are they?

Lets consider what a virus is; It is a computer program, programmed to spread throughout the filesystem of a hard drive. Virus's might delete files or do some other harmful tasks but they always spread. Because of the nature of a virus there are common characteristics which Anti-virus software looks for. Of course there are variations of deadly programs such as Worms.

Because worms spread they're sometimes considered a type of virus. Worms are usually made to harm a network such as spreading copies of it self to other hosts on a network, consuming bandwidth. A good example of a worm would be the Mellisa worm. The Mellisa worm is a Microsoft Word macro worm, which is a program attached with Word document. Mellisa used pre-installed Active-X controls to use Outlook to send copies of itself to 50 people in the users address book! Mellisa determined the users name and used subjects that contained the users name to look as if it was sent by a person. With the infected Word document attached, all the receiver had to do was download the document and 50 more people might have the email in their inbox.

Creating a Virus, Worm, Trojan Horse or Logic Bomb is not very difficult if you know how to program or script. Because of the destructive nature of these deadly programs, it gives a virus writer a feeling of power. However he'll probably feel powerless and foolish when he's in hand-cuffs being escorted to prision. Nevertheless if a virus is efficient and enduring, it'll most likely give the writer short-lived fame.

A battle exists between viruses writers and Anti-virus software developers. New technology might pose new possible spreading methods a virus writer might take advantage of, which is why Anit-virus developers need to know how virus's work and anticipate next generation virus's. In that case, I think it'd be ok to write virus's for the purposes of security with a non-malicious intent, where virus's, worms or etc. are executed in a confined and isolated computer laboratory.

Thus a virus can be visualized as a body of code created to effectively spread itself and attach to other programs. What is scary is that there are virus's that exist that can spread undected by IDS's. Such virus's might push valid instructions to the stack in main memory and when the stack and end of the program meet, the program will continue executing the fresh code pushed to the stack effectively morphing into a different program with different functionality. These virus's are known as Polymorphic virus's.

Overall it is not worth it to write a virus because you want to be famous or respected, or known as an intelligent, dangerous individual because there are many people like that and the fad is fading. You'd be more respected if you helped defend against such malicious endeavors. People respect the hero and despise the villain.