Where computer virus came from?

Computer viruses are called viruses because they share some of the trails of biological viruses. A computer virus passes from computer to computer like a biological virus passes from person to person. Unlike a cell, a virus has no way to reproduce by itself. Instead, a biological virus must inject its DNA into a cell. The viral DNA then uses the cell's existing machinery to reproduce itself. In some cases, the cell fills with new viral particles until it bursts, releasing the virus. In other cases, the new virus particles bud off the cell one at a time, and the cell remains alive.

A computer virus shares some of these trails. A computer virus must piggyback on top of some other program or document in order to launch. Once it is running, it can infect other programs or documents. Obviously, the analogy between computer & biological viruses stretches things a bit, but there are enough similarities that the name sticks. People write computer viruses. A person has to write the code, test it to make sure it spreads properly and then release it. A person also desingns the virus's attack phase, whether it's a sily message or the destruction of a hard disk.