The number of computers being infected for use in botnets has soared in recent months, according to McAfee.
The company said in its quarterly threat report on Tuesday that the number of IP addresses connected to botnet use soared to more than 12 million over the first quarter of 2009. That figure eclipses the previous high set in the third quarter of 2008.
The US and China accounted for more than a fifth of the new infections, with 18 and 13 per cent respectively. Australia was third with 6.3 per cent, followed by Germany with 5.3 per cent and the UK with 4.7 per cent.
The increase in botnet recruitment comes despite lower spam levels compared with the same period last year. However, McAfee researchers suggested that a major increase may be on the horizon.
"The third quarter of 2008 also posted a record number of new zombies, but it was exceeded this quarter by one million," the company said.
"And although spam volume levels have not yet recovered from the McColo shutdown, the activity level of new zombies indicates that the spammers are working hard to regain the infrastructure, and that volumes will return to previous levels soon."
Aside from leading in infection levels, the US was also top in sending spam. Machines from within the US were responsible for more than a third of the global spam load.
"US automakers may be struggling with manufacturing and sales problems, but spam production from the US continues to lead the world, accounting for 35 per cent of global spam output," the company noted.
"Although spam command-and-control operations are an international infrastructure, spammers still favour using computers from the US to manufacture spam."
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