Good article from January 19, 2023 how Telegram is not as secure as some people might think and as they say themselves:
Q: How secure is Telegram? Telegram is more secure than mass market messengers like WhatsApp and Line. We are based on the MTProto protocol (see description and advanced FAQ), built upon time-tested algorithms to make security compatible with high-speed delivery and reliability on weak connections. We are continuously working with the community to improve the security of our protocol and clients.
Point 1 of 7 from the article:
1. Not all Telegram chats are equally secure Let’s go straight to the root of the problem: Telegram is a unique messenger with two types of chats: regular and secret. Regular chats are not end-to-end encrypted. Only secret ones are.No other messenger does this: even the notorious WhatsApp, part of Mark Zuckerberg’s data-hungry empire, uses end-to-end encryption by default. The user doesn’t need to do anything at all, there are no special checkboxes or anything: messages are protected from all outsiders (including the service owners) right out of the box.As for messengers that explicitly position themselves as secure and protected, no one at Signal or Threema would ever think of having two types of correspondence: one end-to-end encrypted, one not. Why bother if you can make all chats equally safe without discombobulating the user? But Telegram is one of a kind.
What do you think where this false sense of security comes from? Because people nowadays expect E2EE? So they just assume that's the case for whatever messenger they use?
I was definitely surprised (after I already used it for a while) when I found out that Telegram is not using E2EE by default.