Virus-like program that spreads automatically to other computers by sending itself out by email or by any other means. A program that propagates itself by attacking other machines and copying itself to the affected machine.
Worms have self-replicating code that travels from machine to machine by various means. A worms first objective is merely propagation. Worms can be destructive depending on what payload they have been given. Worms may replace files, but do not insert themselves into files.
W32.USBWorm spreads through USB drives. Prevents user from using Firefox, shows message which reads, "I DNT HATE MOZILLA BUT USE IE OR ELSE..." The message header reads, "USE INTERNET EXPLORER YOU DOPE." Firefox is then closed by force. Also blocks "Orkut" and "YouTube" sites.