Until a few years ago, 'virus' meant only one thing - a disease-causing organism. Today, the term has yet another meaning.
Computer viruses have been so christened, because they are designed to infect and disable the software in a computer.
A computer virus is a code that is embedded in a computer program. This virus code is transmitted to one or more programs. When the infected program runs, the virus gets activated and destroys or damages software on the computer. The virus gets transmitted from computer to computer, through floppies or through e-mails.
A virus in a computer can cause many kinds of damage. It can stop the functioning of a single computer or networks of computers, damage data and bring work to a standstill.
How does a virus get created? People create viruses. A person has to write the code, test it to make sure it spreads properly and then release the virus. The person also designs the virus's attack phase, which determines whether it's going to be a silly message or destruction of a hard disk. Why would anyone do such a thing? There is no answer to this question. Just as some people throw bombs or shoot at others; some people create viruses to cause mass damage.
More than 80,000 viruses have been created so far. For every virus created, anti virus programmers have worked to make antidotes available, which can "kill" the virus. The anti virus computer programs, detect the virus even as it enters the computer, and destroys it, so that it cannot multiply and spread.