SHANGHAI (NYTIMES) - China has largely blocked the WhatsApp messaging app, the latest move by Beijing to step up surveillance before a big Communist Party gathering next month.
The disabling in mainland China of the Facebook-owned app is a setback for the social media giant, whose chief executive, Mark Zuckerberg, has been pushing to re-enter the Chinese market, and has been studying the Chinese language intensively.
The company's main social media service has been blocked in China since 2009, where its Instagram image-sharing app is also unavailable.
In mid-July, Chinese censors began blocking video chats and the sending of photos and other files using WhatsApp, and they stopped many voice chats, as well. But most text messages on the app continued to go through normally. The restrictions on video, audio chats and file sharing were at least temporarily lifted in the following weeks.
WhatsApp now appears to have been broadly disrupted in China, even for text messages, Nadim Kobeissi, an applied cryptographer at Symbolic Software, a Paris-based research startup, said on Monday.
The blocking of WhatsApp text messages suggests that China's censors may have developed specialised software to interfere with such messages, which rely on an encryption technology that is used by few services other than WhatsApp, he said.
"This is not the typical technical method in which the Chinese government censors something," Mr Kobeissi said. He added that his company's automated monitors had begun detecting disruptions of WhatsApp in China on Wednesday (Sept 20), and that by Monday (Sept 25) the blocking efforts were comprehensive.
Facebook declined to comment, following past practice when asked about WhatsApp's difficulties in China.
Mr Lokman Tsui, an Internet communications specialist at the Chinese University of Hong Kong, said that WhatsApp seemed to have been severely disrupted starting Sunday (Sept 24). But he said that some WhatsApp users might still manage to communicate.
Chinese authorities have a history of mostly, but not entirely, blocking Internet services, as well as slowing them down so much that they become useless. The censorship has prompted many in China to switch to communications methods that function smoothly and quickly but that are easily monitored by Chinese authorities, like the WeChat app of the Chinese Internet company Tencent, which is based in Shenzhen.