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.
JT.Moonwalk is considered to be dangerous. Once it infects the victim's PC, it allows the attacker to gain full access to your computer through IRC channels.
Once this infection have compromised the PC, it will send messages and files to everyone on the victim's Windows Live Messenger contacts. The message reads: "Oh My God !! accept this funny picture !! Look what I found more nude pictures of Justin Timberlake". This is followed by a zip file that infects other machines.