Worms are viruses that actively help themselves spread. Worms are viruses that have a self-replication feature enabling them to spread across the net from one computer to another. Worms are interesting for several reasons, because of their mathematical structure and technological complexity, and because they take the imitation of life forms to another step as they search for computers, penetrate them, and then replicate their intelligence to continue the process. A worm can be contained in any kind of virus including boot, program, and script viruses. Sometimes their inventor will release them into the wild in a single copy, leaving them to replicate by themselves through a variety of stratagems and protocols.
Different worms use different methods to propagate.
Some simply scan the local network drives and folders and insert themselves into programs wherever they can, thereby trusting the human beings to move disks and directories around so they can continue to spread. Once on a new machine, they repeat the process with the new user's email address book, providing opportunities for quickly expanding exponential growth in the number of people reached. Some of the worst outbreaks of email worms have spread around the world within just a few hours, and email remains the worm's fastest known transmission method. However, there are many other types of worms as well. A wide range of other inventive worm strains have been loosed into the wild that employ security weaknesses in IRC , MAPI , sendmail , finger, and other Internet protocols.