Worms often come in the form of a Word document attachment or a similar executable file. They can propagate through email attachment downloads, infected websites, and even P2P file sharing. Worms can remain latent inside a computer system while the user is completely oblivious to its presence.
But, once activated, it can self-replicate and spread to other unprotected server and computers in the same network. A worm infection can spread like wildfire within a short amount of time through the computer network and the Internet.