China is using QR codes to try to control COVID-19. Now, protestors fear the codes are being used to monitor and track them, too.

• China uses a traffic-light system on a COVID app to let people know if they can enter public venues.
• People who recently tried to attend a protest fear the app is being used to monitor and target them.

As part of China's efforts to control COVID-19, provincial authorities have been using a contact-tracing "health code" app to monitor people's movements.

The app works off a traffic-light coding system. The user scans a venue's QR code, and in turn, their own QR code turns either green or red. If green, they have the all clear to enter; if red, they might have COVID-19, and must quarantine.

But a recent wave of protests in Zhengzhou in central China has led some people to fear the app is being used for a different purpose: to monitor and target people who have taken part in these protests.

Questions tracing back to bank protests in Zhengzhou

In April, four local banks in Henan, the province that Zhengzhou is in, announced they would be freezing deposits, cutting off hundreds of thousands of people from an estimated $6 billion of their money, per the BBC.

In recent weeks, people have been taking to the streets in Zhengzhou and Henan, calling for authorities and banks to return their money.

Earlier this week, dozens of people traveled to Zhengzhou to participate in a protest. But upon arriving in Zhengzhou and scanning QR codes at train stations, buildings, or hotels, they said their health codes turned red. People detailed their experiences to outlets including Reuters, Bloomberg, and several Chinese news outlets.

One Beijing-based tech professional, Liu, told CNN he arrived in Zhengzhou on Sunday with a green health code. He was planning to demand that one of the banks release $890,000 of his deposits. But his code flashed red at Zhengzhou's train station, and he was escorted to a quarantine hotel, where he said he saw about 40 other people whose health codes had also turned red.

Zhang, a factory owner from the coastal province of Zhejiang, arrived in Zhengzhou on Monday to join the protest, according to South China Morning Post (SCMP). Zhang said after his health code showed up red at the train station, local police took him to a library, where he was joined by about 10 others who had planned to demonstrate.

Liu and Zhang were escorted back to Beijing and Zhejiang, respectively, by police, per CNN and SCMP.

It's unclear if Zhengzhou authorities used the protestors' codes to prevent them from joining the protests. Henan reported no new COVID-19 cases over the past week, per numbers released by the province's health commission.

A Zhengzhou government hotline was flooded with complaints questioning if the city was targeting people by turning their codes red, per a Tuesday report by state-run Yicai. A spokesperson for Henan's health agency told Yicai that Zhengzhou authorities were investigating the incident.

The Henan Provincial Administrative Approval and Government Information Administration, which oversees the use of digital data across the province, did not immediately respond to Insider's requests for comment. Insider made multiple calls to a hotline number listed on Zhengzhou Big Data Administration's website, but the calls were not put through.

Domestic critics join the chorus of foreign critics

Since the coding system was introduced at the start of the pandemic, foreign critics have voiced concerns that Chinese authorities could use the codes to surveil citizens.

The codes are "yet another way to gather information about people to potentially use it against them in ways which there's no legal basis," Sophie Richardson, the China director at Human Rights Watch, told ABC News in 2020.

But Zhengzhou appears to mark a turning point in that both foreign and local critics have now voiced concerns about authorities' use of the apps' data.

"I would have actually thought this happened more routinely in the past two years but apparently this is a watershed moment for using health tools to crack down on dissent," Alex Gladstein, the chief strategy officer at the New York-based Human Rights Foundation, wrote in a tweet on Tuesday.

Prominent voices among China's establishment have also spoken out.

"If a local government decides to use the health codes for any other purposes other than the specified aim of regulating movement of people, it's a breach of pandemic-prevention regulations, and it damages the public's trust and support for the code and pandemic-prevention efforts. It's not worth the potential threat to our social governance," Hu Xijin, a former editor of state-run Global Times, posted on China's Twitter-like Weibo on Tuesday.