WeChat Monitors Files Shared by International Users to Bolster Censorship in China, Says Citizen Lab

WeChat, a popular messaging app with more than 100 crore users on board worldwide, is monitoring documents and images shared by users registered outside China, to censor these materials from its Chinese users. The app, backed by Internet giant Tencent, silently subjects its international users to surveillance, analysing files shared by them using a remote server, according to a study by Citizen Lab, the research group that earlier revealed the Pegasus attack on WhatsApp.

The surveillance is allegedly used to bolster censorship that WeChat already has for its registered users in China. However, the app doesn't censor content for non-China registered accounts, only monitors them.

Researchers of the University of Toronto's security research group Citizen Lab have determined that WeChat screens documents and images people share through the platform when using phone number not registered in China. The app uses this remote server that conducts the surveillance process, without giving any signs to end-users, according to Citizen Lab. If the server recognises the content as “politically sensitive”, it adds a digital signature in the form of an MD5 hash, to flag that file so that it can be kept away from China-registered users.

In the study, titled “We Chat, They Watch”, the Citizen Lab's researchers noted that multiple tests were conducted between November 2019 and January 2020 to analyse the surveillance behaviour of WeChat. The content screening nature that emerged through the tests wasn't clearly explained in any of the app's privacy agreements and policy documents, the researchers said.

A Tencent spokesperson said that the company takes the Citizen Lab's research seriously and all content shared by the international users of WeChat is "private". Here is the full statement:

"We received the Citizen Lab report and take it seriously.  However, with regard to the suggestion that we engage in content surveillance of international users, we can confirm that all content shared among international users of WeChat is private. As a publicly listed global company we hold ourselves to the highest standards, and our policies and procedures comply with all laws and regulations in each country in which we operate.  User privacy and data security are core values at Tencent, and we look forward to continuing to sustain user trust and delivering great user experiences.”

Real-time censorship using automated surveillance
The study included one instance in which the researchers sent a cartoon of Nobel laureate Liu Xiaobo — an image deemed sensitive in China — from an international account into a chat group with other users also not registered in China.

After that, the researchers sent a second, non-sensitive image using the same MD5 hash of Xiaobo's image into a chat group that included China-registered users. The new image wasn't received by the group members — despite being non-sensitive content. That exemplifies the surveillance system that is purportedly used by the app to censor content for Chinese users.

WeChat's hash index check processes the results in real-time to censor content on the platform without any delay. The automated performance of hash indexing also eases the process of surveillance on non-China registered accounts.

Infamous for censoring content
It is unclear whether the move by WeChat to screen content from non-China registered accounts is politically motivated. A report by The Wall Street Journal dated March 6 highlighted that various social media platforms in China face punishments if any content that is found objectionable by the government overrides their filters.

Earlier this year, Citizen Lab discovered that WeChat blacklisted over 500 keyword combinations related to the coronavirus outbreak, including a text referring to the Wuhan whistleblower Dr. Li Wenliang. The app was also found to censor text for its China-registered users in a report by the research group in July last year.

As per the official data included in the recent quarterly results, WeChat has over 116.4 crore users worldwide. The app has a strong presence in China, thanks to the super-app design that means it's used for everything, from communication services such as payments, shopping, cab-hailing, video conferences, and gaming among others. It initially had good traction in India as well, though WeChat's momentum was lost overtime, as Facebook-owned WhatsApp became the leading messaging app in the country.

Editor's Note: Updated with Tencent's statement. 

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