"It's very difficult to collect evidence against gambling rings. The gambling groups are very sneaky," he said. "And the punishment isn't that severe anyway."

Gathering evidence against online gambling is a big obstacle especially when the gambling rings constantly change servers or open accounts with fake IDs, said Xu Jianzhuo, an official from the Internet security division of the Ministry of Public Security, according to a People's Daily report.

The ministry has had a hotline since 2005 where the public can report illegal gambling.

This March Ren persuaded an entrepreneur in Tianjin, who gambled away 30 million yuan over eight years, to turn himself in to the police. He is still helping the police with the investigation, said Ren.

Ren constantly collects information on bookies and even went undercover last year during the World Cup.

He lost count of how much information he has handed over to the Ministry of Public Security. This week he plans to mail the ministry another bag of documents about the websites, phone numbers, bank accounts and transaction records.

"They can't look into all of them, but I did help with some of the cases," he said.

At the peak of his anti-gambling campaign, thousands of people joined Ren and his "alliance," but now only a couple of hundred people are still actively involved.

"Sometimes I feel it's futile. What I am trying to do? The local authorities aren't doing anything, why am I?" he said. "But once in a while a recovering gambler comes to me and thanks me for helping him, and that's really touching," he said.