Iran blocked Telegram, the most popular messaging app in the country, on Tuesday, claiming the service used by 40 million Iranians endangers national security.

It was just the latest in a series of moves by the Iranian authorities to limit use of the app, part of a tug of war between hard-liners and President Hassan Rouhani, who has long campaigned for more freedom on social media.
https://www.nytimes.com/2018/05/01/world/middleeast/iran-telegram-app-russia.html