A kind of computer virus. After infection, a malicious third party waits for instructions to be sent over the network, steals information from the infected computer, and attacks other computers. Unlike traditional viruses that only move as preset, this name has arrived because a third party can manipulate the infected computer like a “robot” depending on the order to send. Many BOTs operate as programs with administrator authority. Therefore, basically anything you can do with the OS can be done. Most BOTs have functions to read IDs and passwords, send them to third parties, and attack designated Web sites. Multiple computers infected with the same BOT cooperate to sometimes make a DoS attack. Many BOTs have the function of downloading another malicious program from the outside and executing it arbitrarily. With this function, the infected computer can be used as a sender of spam mails and a server for storing malicious files. It can also be a steppingstone to enter another computer. The BOT appeared around 2002 and has increased rapidly since the second half of 2004. Since the source code which is the basis of BOT is published, there are many subspecies which are different from conventional viruses. Anti-virus vendors are at the mercy of successive subspecies BOT at present