In Russia, new problems with Telegram proxies began at the end of May. Formally, the messenger itself is not blocked, but built-in proxies using the MTProto protocol, one of the simplest ways to maintain access to Telegram without separate VPN applications, have been affected.
Previously, such traffic was harder to distinguish from a regular HTTPS connection: it looked almost like browser activity. But in spring, filtering systems began to more accurately recognize MTProto proxies – first by the peculiarities of the TLS connection, and then by other signs: packet size, digital fingerprints, and client behavior.
After the March wave, Telegram updated its applications and made the connection more similar to a browser connection. This helped temporarily, but new restrictions began at the end of May. Now proxies are again unstable: failures occur in waves and manifest in different regions.
For users, this is painful precisely because of the unpredictability. If a message cannot be sent or received here and now, Telegram ceases to be a convenient messenger and increasingly turns into a service for which alternative routes must be sought.
The problem is that this can no longer be fixed with ordinary settings. If filtering is indeed based on deep characteristics of MTProto traffic, new refinement will be required from Telegram. For now, the situation looks like another round of a technical race: some systems learn to recognize proxies, while others learn to better disguise them as ordinary internet traffic.
