Nachi Virus
This morning, the SANS Internet Storm Center posted a note about an increase in ICMP traffic, including a quick initial analysis. As it turns out, yet another worm, this time the W32/Nachi.worm|W32/Welchia.worm, is going around taking advantage of the RPC DCOM vulnerability. The twist this time: the worm will actually clean up machines. It tries to download the correct patches from Windows Update and remove the Blaster worm."