Hackers have taken control of almost 12 million new IP addresses since January, according to a quarterly report from McAfee.

More than 18 per cent of the world's botnet victims were in the US and the number of zombie machines represents a 50 per cent rise over last year. The rise is due to a panic among hackers who needed to recoup spamming abilities after authorities took down a hosting facility last year.

Spam levels dropped about 60 percent after the hosting facility was closed, but researchers said the spam numbers returned to normal as criminals re-build their networks of captured computers. China was the next biggest victim with 13 per cent of victims. The next effected was Australia on six per cent, 5.3 percent in Germany and 4.7 percent in the United Kingdom.

Few victims were based in Russia, which McAfee believes is the home to most of the hackers.