Mydoom was a computer worm that targeted computers running Microsoft Windows. It was first sighted on January 26, 2004. It became the fastest-spreading e-mail worm ever, exceeding previous records set by the Sobig worm and ILOVEYOU, a record which as of 2024 has yet to be surpassed. Mydoom appears to have been commissioned by e-mail spammers to send junk e-mail through infected computers. The worm contains the text message "Andy; I'm just doing my job, nothing personal, sorry," leading many to believe that the worm's creator was paid. Early on, several security firms expressed their belief that the worm originated from a programmer in Russia. The actual author of the worm is unknown. The worm appeared to be a poorly sent e-mail, and most people who originally were e-mailed the worm ignored it, thinking it was spam. However, it eventually spread to infect at least 500 thousand computers across the globe. Speculative early coverage held that the sole purpose of the worm was to perpetrate a distributed denial-of-service attack against SCO Group. 25 percent of Mydoom.A-infected hosts targeted SCO Group with a flood of traffic. Trade press conjecture, spurred on by SCO Group's own claims, held that this meant the worm was created by a Linux or open source supporter in retaliation for SCO Group's controversial legal actions and public statements against Linux. This theory was rejected immediately by security researchers. Since then, it has been likewise rejected by law enforcement agents investigating the virus, who attribute it to organized online crime gangs. Mydoom was named by Craig Schmugar, an employee of computer security firm McAfee and one of the earliest discoverers of the worm. Schmugar chose the name after noticing the text "mydom" within a line of the program's code. He noted: "It was evident early on that this would be very big. I thought having 'doom' in the name would be appropriate."

Technical overview

Mydoom is primarily transmitted via e-mail, appearing as a transmission error, with subject lines including "Error", "Mail Delivery System", "Test" or "Mail Transaction Failed" in different languages, including English and French. The mail contains an attachment that, if executed, resends the worm to e-mail addresses found in local files such as a user's address book. It also copies itself to the "shared folder" of peer-to-peer file sharing application Kazaa in an attempt to spread that way. Mydoom avoids targeting e-mail addresses at certain universities, such as Rutgers, MIT, Stanford and UC Berkeley, as well as certain companies such as Microsoft and Symantec. Some early reports claimed the worm avoids all .edu addresses, but this is not the case. The original version, Mydoom.A, is described as carrying two payloads: A second version, Mydoom.B, as well as carrying the original payloads, also targets the Microsoft website and blocks access to Microsoft sites and popular online antivirus sites by modifying the hosts file, thus blocking virus removal tools or updates to antivirus software. The smaller number of copies of this version in circulation meant that Microsoft's servers suffered few ill effects.

Timeline