The fight has been taken online, and protesters seek secure channels free from government interference where they can organize. Iran’s government has blocked large portions of the internet, including YouTube, Facebook, and VPN services that can circumvent the block. The block is enforced via a combination of centralized censorship by the country’s Supreme Cybercouncil and local ISP interference, resulting in a haphazard system that can still have devastating effects on any service the regime sees as a threat.

Iran’s most popular encrypted messenger has been Telegram. Although cryptographers have criticized Telegram’s homebrew cryptography, local Iranian users care more about the app’s independence from the United States, as the app’s development team is based in Russia, making it less vulnerable to US government requests. The massive group chats made possible by the app are popular.

The government targeted individual users by intercepting account reset messages sent to the user’s phone number.

As protests intensified, Telegram became a tool for organizers, and a target for the regime. Telegram suspended the popular Amad News channel on Saturday, for violating the service’s policy against calls to violence. A conversation that recommended protesters attack police with Molotov cocktails was publicly called out by Iran’s Minister of Technology.

However, Pavel Durov, Telegram founder, alleges that the government also requested suspensions for a number of other channels that had not violated the policy on violence. After Telegram refused, the government placed a nationwide block on the app. The government also banned Instagram.

Government representatives insist the bans are temporary and will be lifted once protests subside.

Signal, which offers group chat features with more robust encryption, is a popular alternative among US activists, but Signal is blocked in Iran for an entirely different reason. The app relies on the Google AppEngine to disguise its traffic through a process called “domain fronting.” This makes it difficult to detect Signal traffic amid the other Google requests. Still, it means that wherever Google is unavailable, Signal is unavailable.
Google appears to have blocked Iranian access to AppEngine to comply with US sanctions. US companies face regulations on technology exported to Iran, and it’s unclear how those rules extend to cloud services like AppEngine.

The blocks leave organizers with no clear way to coordinate activity across groups that often sprawl to hundreds of thousands of people, but although bans have been proposed in the past, WhatsApp is still available in the country.