Dubbed “public opinion analysts,” they work for the Chinese Communist Party’s propaganda department, major Chinese news websites and commercial corporations, according to The Beijing News.

Using keyword searches, their job is to sift the millions of messages being posted on popular social media and microblogging sites such as Sina Weibo, regarded as China’s equivalent to Twitter. They then compile reports for decision makers, the report said.

The number of people monitoring internet activity to prevent criticism of the government and social unrest has been a subject of discussion for years, said David Bandurski, editor of the University of Hong Kong’s China Media Project.