Five suspects from two hacker groups that developed illegal programs and sold time to modify popular online games have been arrested in Sichuan and Anhui provinces.

The groups offered hack tools to enhance the powers of virtual characters in the online games Hero of Gaia and Ministry of War developed by Snail Electronics Co Ltd based in Suzhou.

The investigation began when Snail Electronics found hacker programs called Hero Fairy, Terminator of Hero and Paladin of Empire available for download.

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Game players could download the programs for free, but they had to buy time cards to use them.

For 200 yuan ($30.8) players could use the cheat programs for a year. A month of use was priced at 20 yuan and a week's usage cost 7 yuan.

Time cards for the illegal programs were sold at four online shops hosted by Taobao, the largest online retail site in China.

Suzhou police discovered the hackers were based in Chengdu and Hefei from addresses and bank accounts at their online shops. With the help of law enforcement officials in the two cities, Suzhou police arrested two suspects in Chengdu and three in Hefei during operations mounted in early March.

The suspects said that they decided to hack the two games last May because they were "very popular among game lovers".

"Money must come very easily," they said.

The hackers took in more than 44,000 yuan in less than a year. The largest sale was worth 5,000 yuan.

Paladin of Empire alone - the hack tool for Ministry of War - attracted more than 580 online buyers and brought more than 30,000 yuan.

"Actually a hack tool is only a small problem," said Shi Hai, CEO of Snail Electronics, the first 3D online game developer in China. "But what really matters is that many truly don't realize it's illegal."

Some online game developers even encourage such tools to make their products more popular, he noted.

"In the world of reality, burglary is a crime," Shi said. "In the Internet world, making cheat programs is just like burglary."

Gao Chang, head of the Internet control center for the Suzhou police, said Internet-related infringement is appealing to unethical sellers due to ease of concealment and low costs.

He called for joint efforts by companies, authorities and game players to make a better climate for development and protection of creative work.