Rustock recovers from Christmas hangover.

Spam volumes have returned to normal following a holiday lull that saw a drastic reduction of junk mail.

The Rustock botnet is out of hibernation and back in business, spewing copious volumes of useless junk mail courtesy of hundreds of thousands of compromised Windows machines.

Rustock (which specialises in spamvertising unlicensed pharmaceutical websites) is the biggest single source of global spam. Its return on 10 January resulted in the doubling (98 per cent increase) of global junk mail volumes over the course of just 24 hours, MessageLabs reports.