This definition explains the meaning of a worm. A worm virus can replicate itself and move from computer to computer without a user clicking or running any programs. It moves via file or data transport features such as email, messenger or file sharing. Even if they don’t do any harm, worms can use up your computer processing time and take up your bandwidth as they replicate. However, if worms carry a malicious payload you could end up with deleted or encrypted files or even have a “backdoor” opened in your computer, allowing a hacker to take control of your computer and create what’s called a zombie computer. For example, email spammers often create worms to help send their junk mail, and they send copies of themselves to everyone in your computer’s address book.