China's social media site Weibo finds and deletes controversial posts in near real time despite a daily volume of 100 million messages, researchers say.

Independent researcher Tao Zhu, working with colleagues at Rice University and the University of New Mexico, analyzed censorship practices of Sina Weibo, operator of the Weibo site, which -- like Twitter -- allows users to post 140-character messages with usernames and hashtags.

An estimated 300 million people use Weibo, posting 100 million messages each day.

"Other people have explored censorship on Weibo, but this work is focused on the speed at which censorship happens," Rice computer science Professor Dan Wallach, co-author of the study, said.

The researchers determined operator Sina Weibo uses a combination of keyword-matching software and human censors to monitor and delete potentially controversial posts on Weibo.

By closely monitoring individuals who frequently post controversial messages, Sina Weibo is able to delete many objectionable posts in less than 5 minutes, the study found.

"We have [examined] enough of these posts to be able to run topical analysis algorithms that let us extract the main subjects that Weibo's censors seemed concerned with on any given day," Wallach said.

Weibo faces the challenge of keeping its users engaged -- and thereby looking at advertisements and making money for Sina Weibo -- while keeping the content it hosts compliant with local laws, a challenge all such sites around the world must contend with, Wallach said.

"Weibo gives us a window into the future for what Internet censorship of social media around the world may look like."

Australia's ABC monitoring interference to China signal
Sydney (AFP) March 15, 2013 - The Australian Broadcasting Corporation Friday said it was monitoring interference to its signal into China as Canberra was urged to ensure Beijing does not block international radio news.

ABC International said it supported a statement by the Association for International Broadcasting (AIB) which said English-language programmes from the ABC, BBC World Service and the Voice of America were being jammed in Asia.

In the statement, the AIB said international broadcasts beamed towards China were being "deliberately interfered with by the jamming of a number of frequencies".

"While we have received reports of interference of our signal into China it is extremely difficult to identify or confirm the source of this interference," ABC International said in a statement.

"We will continue to monitor the situation as well as consult with partners in the region."

The state broadcaster said it supported "the free flow of information and objects to the interference of any broadcasters' transmissions", but no formal complaint had been lodged with Chinese representatives.

The London-based AIB said research indicated the source of the jamming, which makes it difficult or impossible to listen to the radio broadcasts, was China.

Australia's opposition leader Tony Abbott said the government must ensure the ABC's service was available in China, the nation's biggest trade partner.

"I don't want domestic censorship and I don't want international censorship ... I think it would be a pity if the ABC couldn't be accessed in China," he said.

"I think the Australian government should do whatever it reasonably can to try and ensure that Australian media outlets are reasonably available."

The government was not immediately available for comment.

The AIB said that Mandarin-language programmes had been interfered with for years, but this is the first time English services had been targeted in a widespread manner.

The association said it would lodge protests with Chinese embassies in Washington, London and Canberra over the disruptions.

Last month the BBC said its World Service shortwave radio broadcasts in English were being jammed in China in a deliberate move by the authorities there to cause "maximum disruption".

The corporation said that while it was not possible to determine the source of the blocking, "extensive and coordinated efforts are indicative of a well-resourced country such as China".