The figures, from security firm Ciphertrust, come amid spiralling rates of internet use in China.
China already has the second biggest net-using population in the world, even though only 8% of its people go online.
Now spam and viruses are becoming big problems, since the government relaxed controls on the net, an expert says.
Net use is growing fast and by 2007 the number of people using broadband in China should surpass those in the US.
But China is not just keeping up on ordinary net use and users, it is also setting the pace on computer crime too.
Typically the hijacked PCs fall under the remote control by malicious hackers when the machines fell victim to a virus such as a worm or Trojan.
Often the controllers of these so-called zombies do not live in the same nation as the machines under their sway.
Ironically much of the spam sent via these hijacked machines may not reach Chinese people at all.
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