Researchers from Harvard and the University of California San Diego released a report in Science in which they explain how to get past the Great Firewall of China.
Gary King and his team created dozens of shill accounts and posted hundreds of messages on China's most popular social networks to see what would be filtered. Then they worked out a way of gaining access to the software used to censor content, so it could reverse-engineer the system.
The group created its own social media website, purchased a URL, rented server space, contracted with one of the most popular software platforms in China used to create these sites, submitted, automatically reviewed, posted, and censored its own submissions.
As a result they had complete access to the software, documentation, help forums, and extensive consultation with support staff and could get recommendations on how to conduct censorship on our own site in compliance with government standards.
What surprised King was that it was OK to criticize the government in China, as long as you are not inciting others to do anything about it.
It looks like the country is more worried about uprisings, protests, and anything that could spur real-life action, not government criticism.
While China is autocratic, King says that it's a "responsive" autocracy, meaning the government is cool with people criticizing their local leaders. In fact, it actually serves the government well if they do so.
Basically if you use a word like “masses," "incident," "terror," "go on the streets," and "demonstration" you are going to be flagged by the censors.
But what is clever about the Chinese censorship system is that it encourages social networking sites to do the censoring for it.
China can maintain the illusion of not censoring posts if it's implemented on a slightly different basis by hundreds of companies throughout the country. At the same time, companies know that they have to censor content that incites people to action, allowing the Chinese government to keep people held down without the illusion that it's actually doing so.