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.
Other botnets have also returned to business following the end of the festive season. For example, the Xarvester botnet has also returned, following a blitz on its command and control servers.
Websense reports much the same dramatic surge on global spam volumes over the same time period between Sunday and Monday, as its chart here illustrates.
MessageLabs and other security watchers remain in the dark over the cause of the Xmas spam "armistice". This isn't a seasonal variation seen in previous years, but something new and thus far unexplained.
One popular theory is that the botmaster controlling spam-spewing machines simply took a break and cracked open the vodka, but there's no real evidence for this.
Nine in 10 of all email messages circulating on the net are spam. ®