The Telegram accounts from more than a dozen Iranians earlier this year were hacked by hackers who managed to intercept the authorization code and text messages. The hackers were able to trace the telephone numbers of 15 million Iranians that use Telegram.
Users can communicate encrypted via Telegram. It is among other things used by activists and journalists in Iran. If users want to log in, an authorization code is sent via SMS from another phone on their Telegram account. It is claimed that Telegram would have 20 million Iranian users.