What is a Virus?

Computer terms are often taken from the non-computer worlds of science and experience, using terms that become metaphors for something happening in the computer world.

In the real world, a virus is a snippet of life that only has life if it joins itself to a healthy cell.  Once inside, it takes over the cell, performs whatever damaging function it does by nature, and uses the cell to replicate itself so it can invade other cells.  A computer virus is a program, usually small, designed to find a home inside your software, sometimes appended to healthy, existing files, sometimes joining the operating system in some way.

What it is there to do is entirely decided by the programmer who wrote it.  Since it would be quite inefficient to have to hack into each computer in the world and try to place the little malicious code there, virus writers program the little bug to replicate itself, passing itself on through various means – emails, messages, attachments, and more.  In addition to the trouble the designer intended to cause, often the virus does other, collateral damage.  This can happen because, unlike commercial software companies, these people have no research and development budget.  They do not have a place to be contacted so they can be informed that their virus is causing problems, and needs to be upgraded.  They simply do not care.  It is in their interest to remain secret in most cases.  Nevertheless, they couldn’t care less if your system is destroyed by the many accidental bad things they cause.  They are criminals, motivated by profit (although some are vandals, just having fun like juvenile delinquents painting graffiti on a water tower).  Other related terms are malware, spyware, adware, trojans, worms and other names each having some distinct meaning of their own, and are so-called because these terms describe what they do or how they propagate.