They are the online equivalent of crime fiction's cleaners - internet erasers who use their connections to purge mainland cyberspace of negative references to troubled companies.
Industry insiders say demand for their services peaks around March 15 - World Consumer Rights Day - each year, with companies keen to cover up substandard products or poor service exposed by the mainland media.
Set up as internet public relations firms but operating outside the law, they can make big money. But the risks are also increasing, and one eraser, who goes by the online pseudonym Mr Unknown, says he is looking for a way out of what has become a cutthroat business.
On the mainland it is not just government that censors negative reports or promotes positive online postings. Mr Unknown, a partner in China News Communication Net, says the erasure of online posts became an industry on the mainland around 2005 and blossomed two years later as the number of internet users boomed.
The mainland had 384 million internet users in December, almost double the number at the end of 2007.
Mr Unknown entered the industry in 2008 and his firm's online introduction boasts of connections with many mainland websites, including portals, official websites and forums, from which it can erase digital information.