I heard about some kind of "FSB hack", is everything fine?The Telegram Team
To this day no ways of undermining Telegram's encryption have been discovered. We are continuously working with our worldwide community of developers and security specialists to keep it this way.
Telegram's protocol specification is open (detailed description, overview). Our app code, which together with the docs allows to fully evaluate the end-to-end encryption implementation, is also open. Security researchers have all the necessary tools to evaluate Telegram's protocol, and we offer bug bounties and periodic contests to attract attention and scrutiny to what we do.
So what happened?
A scare story surfaced recently, claiming that some unnamed "ex-operative" heard from some other unnamed "agent" that the FSB has "cracked" Telegram. This story is actually a part of an "intelligence report" that has been touring the journalistic circles since June 2016 and is very likely to be fake. Here's a nice article about it from The Guardian: https://www.theguardian.com/media/2017/jan/10/buzzfeed-publishes-donald-trump-russia-documents-ethics-questions
If the report is not fake (and the majority of experts agree it is), it probably refers to the story of SMS interception for two Russian oppositionary accounts that were not using 2-Step Verification. Check out this Fortune piece for details: http://fortune.com/2016/05/06/telegram-activists-hack/.
So what do I do?
Check out this FAQ article if you want to learn more about 2-Step Verification: https://telegram.org/faq#q-how-does-2-step-verification-work
As for the report, bear in mind that Journalists from the Guardian, the Financial Times, and other reputable papers have had it for many months and to this day they are unable to confirm a single statement from it.
Keep calm and send Telegrams!