Watch what you say (Image: VIEW CHINA PHOTO/Rex Features)

The way the Chinese government censors and deletes politically-sensitive terms online has been revealed for the first time.

As expected, the communists are hypersensitive to criticism of the state – but also to people slating the so-called ‘Great Firewall’, the network blocking technology that prevents Chinese people browsing the internet freely.

The US study also shows Beijing’s censorship machine works in real time – and can adapt quickly to emerging issues. It’s also location-dependent, being far more active, when required, in dissident regions.


David Bamman, a computer scientist and linguist at Carnegie Mellon University in Pittsburgh, got the idea for the research last summer when he noticed how quickly false rumours of the death of former Chinese president Jiang Zemin disappeared from China’s Twitter equivalent Sina Weibo.

“I went to check back on some of those messages and it really shocked me to discover that around 70 per cent of them had been deleted,” Bamman told New Scientist. So with colleagues Noah Smith and Brendan O’Connor he decided to study the censorship mechanism more closely.

They took advantage of the fact that Sina Weibo , China’s biggest commercial microblogging network, publishes an interface to encourage developers worldwide to devise smartphone apps that allow Chinese-speaking people anywhere to read and post Twitter-style 140-character messages.

This interface allowed the Carnegie team to download nearly 57 million messages from Sina Weibo between 27 June and 30 September. Once they had these, they then examined Sina Weibo’s archive to see which were later deleted. “We could then see which terms in a message meant it had a higher chance of being deleted,” says Bammam.

As might be expected, criticism of state propaganda was not tolerated. Messages attacking China’s “Ministry of Truth” were zapped, as were ones involving calls for the “resignations” of incompetent government officials, such as that of the railways minister after a horrific train crash . Complaints about Fang Binxing – architect of the web censoring Golden Shield Project, nicknamed the Great Firewall – were also highly deleted – as were mentions of a pair of Communist Party meetings which became a code word for arranging pro-democracy protests last spring.

Interestingly, at least once the censorship seemed to work for the social good: when a false rumour started that eating iodised salt, rather than potassium iodide pills, would protect people from radiation leaks from the Fukushima Daiichi nuclear power station, the censors deleted the messages.

“What was also interesting was that messages you’d expect to have been deleted all the time – like mentions of the Falun Gong [spiritual movement] or the dissident and artist Ai Weiwei – were not done so every time. It would seem to suggest that there is no automatic, blanket deletion going on,” says Bamman. Rather it points to a high level of human involvement and a nuanced approach.

The censorship mechanism is also agile – able to turn its attention to troublespots on demand. “This is the most surprising thing that we saw,” says Bamman. “In Tibet there was an overall deletion rate of 53 per cent – against 12 per cent in Beijing and 11 per cent in Shanghai.” The research will be published in a forthcoming issue of the open access journal First Monday .

Pádraig Reidy of the London-based pressure group Index On Censorship says the research throws new light on Chinese information control: “This study displays the remarkably hands-on nature of Chinese political censorship. While we tend to think of communist party censorship purely in terms of the ‘firewall’ – blocking external content – we can now see the intense and swift nature of internal censorship.

“This suggests incredibly close, real-time, manned monitoring of discussions and searches. We know that the Chinese government has thousands of people working on web censorship. This study proves how serious a project that is for the regime.”