On January 26, 2004, security experts detect an email worm called "Mydoom," which quickly becomes the fastest-spreading of its kind. Within two days, the British security firm MessageLabs identifies more than 1.8 million copies of the virus circulating in 168 countries.
Computer viruses date back to 1971, when engineer Bob Thomas created the “Creeper,” a self-replicating worm that displayed the message, “I’m the creeper: catch me if you can.” Designed as an experiment, the Creeper did not harm the computers it infected. Many viruses that followed, however, were deliberately malicious.