The Zindos worm, which uses MyDoom.M-infected computers to launch a denial of service attack on www.microsoft.com, is having no visible effect thus far on the performance of Microsoft's web site. The worm is installed through backdoors on a network of machines compromised by the MyDoom.M virus, which disrupted the performance of search engines earlier this week.

Once Zindos installs itself, the host machine is programmed to commence an immediate DDoS on Microsoft, unlike earlier MyDoom variants with trigger dates for electronic attacks.

Microsoft has previously weathered DDoS attacks from substantial bot networks compromised by MyDoom.B, MyDoom.C/DoomJuice and MyDoom.F. Variants of MyDoom have had more success in DDoS attacks against The SCO Group and the Recording Industry Association of America, but continue to target the sturdier defenses of the Microsoft site.