Before understanding what a computer virus is, it is necessary to understand what a virus in when it occurs in a living form (such as a human body, an animal, or a plant).
A virus is a small organism that is only able to reproduce itself within another living cell or body. It is typically harmful to the cell or body in which it lives, and is the cause of many illnesses and diseases. The word virus comes from Latin and literally it means "poison." So basically it is a "poison," able to reproduce itself within another cell or body. An example of an illness caused by a virus is the flu.
How does this relate to computers? Well basically, a computer virus is a harmful computer program which will damage files or your computer, and which is able to duplicate and spread itself within a computer or computer network. Usually the computer virus is hidden within a program, file or document.
Criminals, or somewhat talented idiots with nothing better to do with their time, create computer viruses and spread them to other people's computers. The sole purpose of this activity is to create trouble and damage.
Similar to a common virus like the flu (which spreads from person to person), the computer virus has the ability to spread and "infect" other computers, files or documents. A computer virus can spread itself through files and documents; such as word-processing documents, spreadsheets, emails, computer programs etc. It can spread itself through the Internet and through local computer networks, as well as through removable storage devices such as memory sticks and floppy disks. Because it is hidden, it is hard to detect. It can be spread to other computers, unknowingly, by the computer user.
What exactly does a computer virus do? Well, it works similarly to viruses (like the flu) that make a person sick. A computer virus will make your computer "sick". What a virus will do to your computer depends on what it is programmed to do. Some can be very harmful, while others are made to simply annoy.
A wide variety of names have been made up, in order to describe different types of computer viruses. Some examples are as follows (you may click on these terms for a more detailed description of what they are):
Understanding the basics of what viruses are is the first step to learning what to do about them, and how to be completely in control of your computer's security. I hope this information has been of use to you.