Microsoft says Conficker infected or tried to infect 1.7 million PCs in the fourth quarter of 2011. Worm first appeared in fall of 2008, exploiting a just-patched Windows vulnerability. Microsoft calls Conficker the number one threat in the enterprise for the last two-and-a-half years. The worm’s working group has been blocking the worm’s command and control domains since 2009. The current size of the Conficker botnet — those PCs now infected — is approximately seven million, Microsoft claims.”]

