Miscreants are taking advantage of slowness in patching systems with an emergency Windows security fix issued late last month to spread malware.

Exploit toolkits for the MS08-067 are dropping bots that turn compromised machines into drones in a DDoS attack network, among other attacks. The attack code, thought to originate in China, takes advantage of a flaw in Windows RPC code to weave its evil spell.

Microsoft patched the vulnerability with an out-of-sequence patch on 23 October. Trojans exploiting the flaw were spotted the day afterwards. Analysis of these strains suggested they may have been in circulation before Microsoft issued its patch.

Things have since kicked up a gear with reports of the KernelBot DDoS attack tool as well as other separate reports, via the SANS Institute's Internet Storm Centre, that worms based on the vulnerability are circulating in the wild. Symantec rates the Wecorl worm as a low-risk threat.

The latest worm attacks are distinct from the earlier Trojan attacks, and low level. By comparison the Blaster (aka LoveSan worm) - which exploited an earlier flaw in Microsoft's RPC technology five years ago - caused widespread infection and system instability. ®

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