A computer virus is a malicious computer programA virus is just a program, but it's written by a person of questionable character who wants to do harm. It's made up of lines of programming instructions and runs like any other program.
...an unsuspecting human...For a virus to be successful, it has to be executed on a computer by a human. That means a file has to be opened, a program has to be run, or a computer has to be booted. In other words, programming code has to be run by a human action. That could be you, me, friends, or family anyone who uses a computer. This is not to say that anyone executes a virus on purpose. Usually we're tricked into it. But a virus requires a human's help to proliferate. Remembering this fact goes a long way to preventing viruses from ever running a muck on your computer.
How Does It Spread?
To steal a little lingo from Star Trek, replicating is a virus's prime directive. For a computer virus to be successful by any definition, it must clone itself, make its way into other computers, and repeat the replication cycle. This is how it spreads. Of course, it uses many tricks to do this, including riding on other programs' backs, moving in email as a file attachment, and even downloading from a web page. Virus writers use many methods to move a virus between computers, but you can categorize them into two types:
External media Any storage device that can contain a computer file, such as a floppy disk, DVD, or CD, and be connected or inserted into a computer.
A network connection A network is a group of computers connected so they can exchange data. The Internet, which is the most common source of viruses these days, is a large network. Viruses can use the connection to move in chat, in email, via the Web, and via specialty computer-to-computer connections.
In 1984, University of New Haven professor Fred Cohen first used the term computer virus in a research paper "Experiments with Computer Viruses." Although Cohen is sometimes credited with coining the term, he credits theoretical computer scientist Leonard Adleman with inventing the term.
Now you know What is a Computer Virus? and How A Computer Virus Works. Don't you want to know What Can A Computer Virus Do To Your Computer? I know you do!