The amount of malware coming from China rose 153 percent during the last six months of 2005 according to Symantec.

The increase came in remote-controlled "bot" attacks emanating from China during the period, said Dave Cole, a director with Symantec Security Response. Bot attackers use malicious software like viruses to seize control of computers, which are then used to launch further attacks.

The number of bot-infected computers in China rose 37 percent during the period, although the US has the highest number of such machines. "Broadband adoption [in China] appears to be driving bot-directed attacks as well as bot infections. That's one of the big things we saw in this report," Cole said.

Rising Internet use in China, and a lack of precautions taken by new users, may be contributing to the malware jump.

"Just like the rise of servers hosting international e-mail spammers in China, malware hosting sites in China have also been on the upswing," Danny Levinson, managing partner at BDL Media, an online media publisher in China. "The problem is that computer users all over the world are inevitably lazy, and therefore prone to getting infected."

(Steven Schwankert, in Beijing, contributed to this report.)