Iran has been smarting under an economic crisis since the most recent round of American sanctions banning Tehran’s oil sales: Some estimates suggest that inflation is around 40 percent, unemployment is at 14 percent, the economy is expected to contract by 9 percent and the Iranian currency has lost more than half of its value against the dollar since the Trump administration reimposed sanctions.

In Tehran, Waze users were sending traffic reports calling for protests. My relative followed one to a spot on Sattari Highway, an expressway running from northern to southern Tehran. She shared her photographs and videos from the protest with me and some mutual friends on a social media chat. Hundreds of cars stopped on the highway, and people were protesting. Tires and garbage cans were on fire around her.

After she got back home, she expressed her surprise that the internet was still working and we were able to communicate. Hamrahe Aval, or the Mobile Telecommunication Company of Iran, a mobile phone and internet service provider with more than 50 million subscribers, had stopped working on Saturday morning in Tehran. Her Irancell network was still connected, though working at a slower speed. By the afternoon I lost touch with her.

Tehran is now able to shut down internet access to tens of millions of people within a day. Ninety-three percent to 95 percent of all internet users in Iran were offline within 24 hours of the shutdown, according to one report, the exceptions being the organs of the government and some public universities.

Internet shutdowns are costly for a nation’s economy. NetBlocks and The Internet Society estimate this one could cost Iran about $370 million a day, but Tehran is likely to have diminished financial loss by relying on its National Information Networ k , a domestic digital infrastructure sometimes referred to as the “national internet” or “halal net.”