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.
Tanya Babe sends messages to users in Windows Live Messenger. The messages contain links to help spread the infection. Once this infection have compromised the PC, it will send messages to everyone on the victim's Windows Live Messenger contacts.