Police in central China have shut down a hacker training operation that openly recruited thousands of members online and provided them with cyberattack lessons and malicious software, state media said Monday.

The crackdown comes amid growing concern that China is a centre for internet crime and industrial espionage. Search giant Google said last month its email accounts were hacked from China in an assault that also hit at least 20 other companies.

Police in Hubei province arrested three people suspected of running the hacker site known as the Black Hawk Safety Net that disseminated website hacking techniques and Trojan software, the China Daily newspaper said. Trojans, which can allow outside access to a computer when implanted, are used by hackers to illegally control computers. The report did not say exactly when the arrests took place.

Black Hawk Safety Net recruited more than 12,000 paying subscribers and collected more than seven million yuan ($1.1 million) in membership fees, while another 170,000 people had signed up for free membership, the paper said.

The report said police seized nine servers, five computers and a car, and shut down all websites involved in the case. Authorities also froze 1.7 million yuan ($266,000) in assets.

The shutdown of the site followed an investigation involving 50 police officers in three other provinces, the local Changjiang Times newspaper said.

The case can be traced to a hacking attack in 2007 on an internet cafe in Macheng city in Hubei that caused web services for dozens to be disrupted for more than 60 hours, the paper said. A few of the suspects caught in April said they were members of the Black Hawk Safety Net.

Backup site said to be working

Black Hawk's website 3800hk.com could not be accessed, but a notice purportedly from Black Hawk circulating on online forums said that a backup site had been set up. The notice also sought to reassure members of its continued operations and said its reputation was being smeared by some internet users.

"At this time, there are internet users with evil intentions who have deliberately destroyed Black Hawk's reputation, deceived our members and stole material," the notice addressed to members said. "We must join forces and attack these websites."

A customer service officer contacted by phone, who refused to give his name, said the backup site provides content for its paying members to download course material to allow them to continue their computer lessons — though not in hacking.

The Hubei government refused to comment Monday while officials at the provincial public security bureau did not respond to repeated requests for comment.

Google threatened last month to pull out of China unless the government relented on censorship, an ultimatum that came after the search giant said it had uncovered a computer attack that tried to plunder its software coding and the email accounts of human rights activists protesting Chinese policies.

Government officials have defended China's online censorship and denied involvement in internet attacks, saying the country is the biggest victim of web attacks. The Ministry of Industry and Information Technology said hackers tampered with more than 42,000 websites last year.

Meanwhile, scrutiny of Chinese internet security grows following a rash of attacks traced to China and aimed at a wide array of U.S. and European targets, including military contractors, banks and technology companies.

Security consultants say it is hard to know what proportion of hacking from China is the work of individuals and whether the government is involved. But some say the high skill level of some attacks suggests China's military or other agencies might have trained or directed the hackers.

"The scale, operation and logistics of conducting these attacks — against the government, commercial and private sectors — indicates that they're state-sponsored," security firm Mandiant Corp. said in a report last month. "The Chinese government may authorize this activity, but there's no way to determine the extent of its involvement."