A computer worm is a program that travels across a computer network replicating or reproducing itself as it goes – in other words, they spread over the internet. Computer worms are considered much worse than computer viruses.
Computer worms vs Computer Viruses
Viruses tend to infect files or programs and spread that way. They rely on your behavior to spread – in other words, you have to actually open the document, or run the program to become infected. Worms on the other hand travel from computer to computer and do not human help quite as much to spread. The prime example of a worm is an infection that sends copies of itself to everyone in your email address book.