Some tech media reported that the Telegram Desktop app wasn’t secure because it “leaked IP addresses” when used to accept a voice call.
The reality is much less sensational – Telegram Desktop was at least as secure as other encrypted VoIP apps even before we improved it by adding an option to disable peer-to-peer calls. As for Telegram calls on mobile, they were always more secure than the competition, because they had this setting since day one.
During a peer-to-peer (P2P) call, voice traffic flows directly from one participant of a call to the other without relying on an intermediary server. P2P routing allows to achieve higher quality calls with lower latency, so the current industry standard is to have P2P switched on by default.
However, there’s a catch: by definition, both devices participating in a P2P call have to know the IP addresses of each other. So if you make or accept a call, the person on the other side may in theory learn your IP address.
That’s why, unlike WhatsApp or Viber, Telegram always gave its users the ability to switch off P2P calls and relay them through a Telegram server. Moreover, in most countries we switched off P2P by default.
Telegram Desktop, which is used in less than 0.01% of Telegram calls, was the only platform where this setting was missing. Thanks to a researcher who pointed that out, we made the Telegram Desktop experience consistent with the rest of our apps.
However, it is important to put this into perspective and realize that this is about one Telegram app (Telegram Desktop) being somewhat less secure than other Telegram apps (e.g. Telegram for iOS or Android). If you compare Telegram with other popular messaging services out there, unfortunately, they are not even close to our standards.
Using the terminology from the flashy headlines, WhatsApp, Viber and the rest have been “leaking your IP address” in 100% of calls. They are still doing this, and you can't opt out. The only way to stop this is to have all your friends switch to Telegram.