The number of compromised zombie PCs has shot up by almost a quarter (23 per cent) over the last week because of the release of a new computer worm variant, according to security appliance firm CipherTrust.

CipherTrust Research Labs has identified an average of 265,000 zombies per day since the release of the latest Mocbot worm variant, which is exploiting the MS06-040 Windows vulnerability announced on 8 August in order to spread.

The junk mail cohorts of hackers are using Windows PCs infected with the worm to step up spam campaigns, according to CipherTrust. "Mail volumes have once again reached a high this week, with spam making up 81 per cent of the traffic. Much of this increase can be attributed to the spam originating from the new zombies unleashed by the Mocbot worm," said Ed Rowley, a technical consultant at CipherTrust.

The Internet Storm Centre has compiled a helpful list of recommendations to assist in repelling this botnet threat, which can be found here. ®