Computer worms are malicious computer programs that infect computers connected to a computer network. A user unknowingly allows computer worms to enter his computer by opening an email attachment with executable scripts.
Once inside a computer, computer worms replicate themselves and often generate more email messages containing copies of themselves. Robert Morris invented the first self-replicating program on Nov. 2, 1988, and released it to the Internet without any malicious intent. However, computer worms are now used by criminals to steal the confidential information of users and to control computers for sending spam email or attacking business and government computers.