The craze in online games among Chinese netizens is fueling an increasingly lucrative market for computer hackers, security firms have said.

"There is a huge underground market and major revenue comes from selling game accounts or virtual items stolen from hijacked computers," said Zhang Yumu, vice-president of Beijing Rising International Software Co, one of the largest domestic security firms.

A recent report by State broadcaster CCTV said that Trojan horse attacks, which allow hackers remote access to a targeted computer system, are making up a market that is expected to be worth 10 billion yuan ($1.4 billion) this year.

The CCTV report, aired on Wednesday, cited a hacker saying he could get hundreds of thousands of yuan every month by hacking into computers and stealing the user's personal information and game account.

The hacker would then log into the game account and transfer all the valuable virtual items such as weapons and clothes and sell them through online sites, according to the report.

The hijacked computer's accounts were later sold for other uses, such as participating in online attacks and piling up false traffic data.

Trojan horse attacks have became a major online threat in China in the past few years, accounting for more than 95 percent of all the online attacks in the country, according to figures from online security firms.

Zhang from Rising said the number of Trojan horse attacks surged 10 times last year in China and the number is expected to further increase 60 percent this year.

But he does not think the whole market turnover is as high as 10 billion yuan, estimating that the real market value is about 100 million to 1 billion yuan.

"The rise of the attacks increased in line with the rise of online games in China," he said, noting that over 95 percent of the revenue of the Trojan horse attackers came from selling online game accounts and virtual items.

Sales revenue of China's online game market grew 76 percent in 2008 to 18.3 billion yuan, according to government figures, making it one of the few industries that was not impacted by the world's economic slowdown.

Online gamers in China grew 22 percent to 49 million last year.

The number is expected to grow to 94 million by 2013, with industry sales revenue hitting 39 billion yuan.

Tie Jun, an engineer from Kingsoft, one of China's largest security firms, said online games companies in the country had not shown great interest in the past in prohibiting the trade of game accounts and virtual items in the underground market.

But with joint efforts from online gaming and security firms recently, the growth of Trojan horse attacks is seeing signs of slowing down, he said.