Unicle

Unicle is an Internet worm that spreads by e-mail. It comes in infected messages and installs itself to the computer immediately after a user opens such message. Then it uses own mail server to send copies of itself to addresses found in a computer. The worm contains a backdoor, which allows the attacker to control an infected PC remotely. However, Unicle doesn't work in all environments: it was designed to work on Chinese version of Windows operating computer and most likely will not be able to install itself on other versions of the OS.