ARI SHAPIRO, HOST:
Who is spying on us, and how? We're trying to answer those questions in this month's All Tech Considered.
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SHAPIRO: It's well known that China screens its citizens' social media accounts and personal messages. Now people outside China say the same thing is happening to them. NPR's Emily Feng reports.
EMILY FENG, BYLINE: Activist Zhou Fengsuo was a student leader in the 1989 pro-democracy protests in Beijing's Tiananmen Square. When the protests were crushed, Zhou went to prison, then political reeducation, before moving to the U.S. in 1995. Today, he lives in a quiet Puerto Rican New Jersey neighborhood, and China's most popular social media app, WeChat, is his main link back to China. He's in constant communication with hundreds of people in China, advocating for political prisoners.
ZHOU FENGSUO: I have so many groups. It's probably less than a hundred but more than 50.
FENG: But in January, he noticed something strange. People weren't responding to his WeChat messages.
ZHOU: I probably realized because I was expecting some feedback and there was no feedback.
FENG: It was then he realized his messages were being censored so no one ever saw them. China routinely uses WeChat to censor Chinese Internet users, but now people outside China are also getting caught up. Dutch cyber researcher Victor Gevers thinks he knows why. He scans the Internet for vulnerabilities, and sometimes he finds odd things, shocking things, like a Chinese database containing 3.7 billion WeChat conversations collected on a single day. Some 19 million of the messages were sent by people outside of China. Some messages then were censored. Other bits of the database made Gevers wonder exactly what was going on.
VICTOR GEVERS: Why are there persons identified there with their ID number? Why is this database being built like that? Why are these messages being flagged?
FENG: Here's how it worked. Gevers told me anyone using WeChat to send sensitive phrases would have their entire conversation scraped into this public security database no matter where they were in the world - phrases like Tiananmen, Xi Jinping. If the user is in China, the database automatically alerts the nearest Chinese police station. Tencent, WeChat's owner, declined to comment. And the database was completely unprotected, meaning anyone online could change its contents.
Gevers is still trying to figure out why WeChat archived these specific messages.
GEVERS: Who builds a mass surveillance system that is open to the Internet and you can enter without any username or password and change the data? That's horrible.
FENG: For years, cybersecurity outfit Citizen Lab at the University of Toronto has tracked how WeChat uses keyword algorithms to automatically identify sensitive phrases the app then censors. Here's Jeffrey Knockel, a postdoctoral fellow at the lab.
JEFFREY KNOCKEL: Chat filtering on WeChat applies to anyone who has created a WeChat account using a mainland Chinese phone number. This means that even if you move to another country and switch your WeChat account's phone number to that of that country, the censorship will still apply to you.
FENG: But Chinese tech companies like Tencent, WeChat's owners, now have millions of international users, expanding who China can surveil. Sarah Cook is an analyst at nonprofit Freedom House. She points out WeChat is used abroad not just by Chinese tourists but also politicians in democracies communicating with Chinese constituents and dissidents.
SARAH COOK: Maybe they're communicating with somebody else who's outside of China who has reached out, but they're still, for the most part, operating under the rules that are inside China.
FENG: And those rules are leaving American WeChat users confused and scared about why they were blocked.
DAVID: Although I was able to read the other people's messages, when I posted my message and nobody can see it - like I'm not there.
FENG: That's David, a doctor who has lived in the U.S. for almost three decades. He doesn't want to use his full name because his family still lives in China. Like Zhou Fengsuo, his WeChat group messaging was blocked as well, then reinstated when, he says, he stopped sharing political articles. He self-censors now.
DAVID: This censorship has just affected me psychologically and my behavior - both.
FENG: Back in New Jersey, the activist Zhou Fengsuo is not giving up on WeChat. He says his activist work depends too much on the app.
ZHOU: I have to use it. I just have to know what's going on.
FENG: Even if, he adds, doing so can be very dangerous.
Emily Feng, NPR News, Beijing.
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