They formed a so-called "corpse network," an attack tool popular among Internet hackers, which can prevent other computers from regular Internet service or send out mass junk e-mails on the hacker's order.
The machines were used to perform denial of service attacks, and may have been involved in identify theft. Chinese authorities have apprehended the man and accused him of the computer crimes.
The Ministry of Public Security said coordinated hack attacks were manipulated by the hacker after he gained access to the PCs through the use of a virus. Up to 40,000 of affected machines may be abroad, the Ministry said.