Today marks the first anniversary of the MyDoom combined virus and spamming threat, which infected millions of desktops around the world.
At 13.26pm on 26 January 2004 security software company MessageLabs intercepted its first copy of W32/MyDoom.A.
Within 24 hours MessageLabs stoped more than 1.2 million copies. Other security managed services suppliers recorded similar levels of attack.
MyDoom.A, which achieved a peak infection rate of one in 12 e-mails, represented a landmark in the history of computer viruses, according to MessageLabs.
It was not the first worm to demonstrate how virus and spamming techniques could be effectively combined, but it was the most successful and encouraged other attackers to copy it, said MessageLabs.
When launched, the mass-mailing worm also spread via file sharing service KaZaA and had the ability to randomly generate or guess likely e-mail addresses to send itself to.
The combination of these methods ensured that 12 months on it was still the most widespread virus outbreak of 2004, said MessageLabs. The MyDoom family now comprises of more than 30 variants to date.
Alex Shipp, MessageLabs' senior anti-virus technologist, said, "MyDoom.A represented a step change in the virus landscape."