The Chinese government is using the massive amount of data it has collected to categorize people according to their likelihood of infection by the new coronavirus. But some people say they have been incorrectly tagged and forced into quarantine.

On Valentine's Day, a 36-year-old lawyer in eastern China discovered he had been coded "red."

The lawyer, Matt Ma, was effectively put in chains. The color, displayed in a payment app on his smartphone, indicated that he needed to be quarantined at home even though he was not sick.

Without a green light from the system, he could not travel from his home village to the eastern city of Hangzhou, or make it past the checkpoints that have sprung up across the city as a measure to contain the new coronavirus.