In a series of raids, police arrested 8,900 suspects involved in everything from net fraud to online pornography.
China said the raids were carried out in an effort to "purify the network environment".
The raids also shut down a fake PR operation that threatened to post bad reviews of products and services unless it was paid to keep quiet.
The raids are the latest in a series that China has mounted against "harmful and illegal" elements online. Earlier operations have tackled internet cafes but the latest round has been aimed specifically at thieves and conmen.
Police say hackers who stole online identities, cyber-thieves who targeted banks as well as virus writers were all grabbed during the raids.
About 4,400 criminal cases were likely to result from the operation, said the police.
The raids, carried out over the past couple of months, tackled gangs in many different parts of China including Beijing, Jiangsu, Zhejiang and many other regions. Homes, offices and warehouses were hit, with police grabbing fake designer goods and counterfeit drugs as well as firearms and bullets.
In addition to tackling criminals, the long-running operation has also led to the removal of 188 million articles and comments from websites and chat forums that police deemed to be "harmful".
Chinese police have broken up more than 700 gangs who were using the web for criminal ends.