As the death toll from days of ongoing protests climbed to at least 21, Telegram has remained intermittently blocked in the country. Some 40 million Iranians, totaling about half of the population, use the app. Its encryption allows them to talk to each other away from the eyes of their government.

Also blocked were Instagram and Signal. Iranians woke up in the New Year to find themselves cut off from one another in a country that already ranks close to the bottom when it comes to political rights and civil liberties.

Sanam Vakil an associate fellow at Chatham House says that the Iranian government has a lot of experience with censorship. “It’s about preventing networking and preventing people from making meaningful connections,” she says. Iran bans YouTube, Facebook, Twitter and the BBC Persian services, and Iran is said to have one of the strictest internet censorship policies of any country in the world.

Oliver Farnan, a cybersecurity doctoral student, at the University of Oxford in the UK says, “All of their internet goes through internet exchanges controlled by the government, so it generally makes it a lot more straightforward to block things.”

The Iranian government can cut off access to a website by just adding the site’s IP address to their list of blocked websites. “It’s become the standard play for governments in these situations,” says Farnan.

It is possible to visit blocked websites by using VPNs or Tor software, but only a small number of Iranians seem to be using this technology. On Tuesday there were around 12,000 people in Iran using Tor software says Joss Wright at the Oxford Internet Institute, which is only a tiny portion of the country’s 56.7 million internet users.

Wright adds that without a large number of people using a website, that site’s usefulness is affected. “If 99 per cent of the internet can’t get to Instagram there’s not much point people accessing it at all,” he says.

Telegram, created by Pavel Durov has been very successful in Iran. The app is a hybrid of a messaging app and a social media feed. It allows people to talk directly with each other or subscribe to public channels. When one of those channels started calling on subscribers to use firearms against Iranian police, Telegram took the channel offline because it violated its terms of service. Still, Durov only did that after Iran’s ICT Minister tweeted, asking him to do so. The minister, Mohammad-Javad Azari Jahromi, demanded that Durov starts blocking “terrorist channels” of people opposing the regime. “If Telegram[‘s] manager does not respect Iranians’ demand, the application will be closed completely,” he said, according to the state-backed news agency IRNA.

If Durov doesn’t make concessions to the Iranian government the app may be banned for good in the country. “It’s easy for them to be blocked,” says Farnan. “So they either have to deal with [that] or make some kind of agreement with the government.”

Durov recently tweeted, “We don’t care about complying with local laws. We care only about applying our own rules fairly and equally to all public content on @telegram.”

Just using certain apps can be enough to attract the attention of the state. “They’ve identified individuals and gone after them having tracked them on Telegram and Instagram,” says Vakil. As well, he says it’s not just protesters who are using new technology to rally people to their cause, but in fact, the Iranian government sent messages to people’s smartphones, urging them not to take part in the protests.