It would make 'one big badass botnet,' says Finnish security companyThe computer worm that exploits a months-old Windows bug has infected more than a million PCs in the past 24 hours, a security company said today.

Early Wednesday, Helsinki, Finland-based security firm F-Secure Corp. estimated that 3.5 million PCs have been compromised by the "Downadup" worm, an increase of more than 1.1 million since Tuesday.

"[And] we still consider this to be a conservative estimate," said Sean Sullivan, a researcher at F-Secure, in an entry to the company's Security Lab blog. Yesterday, F-Secure said the worm had infected an estimated 2.4 million machines.

The worm, which several security companies have described as surging dramatically during the past few days, exploits a bug in the Windows Server service used by all supported versions of Microsoft Corp.'s operating system, including Windows 2000, XP, Vista, Server 2003 and Server 2008.

More Here