'Good' worm fights MSBlast
Instead of crashing computers and attacking Microsoft, a new variant of the MSBlast worm downloads relevant patches
A variant of MSBlast spread on Monday, but the new worm has an odd twist: it applies a patch for the vulnerability that it and other MSBlast worms use to infect Windows systems.
The new worm, dubbed W32.Welchia, W32/Nachi and Worm_MSBlast.D, appears to properly download the patch for both Windows 2000 and Windows XP from Microsoft's Web site. Moreover, the variant will delete itself the first time an infected computer starts up in 2004.