Deep Packet Inspection (DPI) blocks Telegram by recognising the unique byte signatures of its transport protocol. Standard MTProto uses a fixed 0xEE prefix on the first packet and specific handshake patterns – easy for state-level filters like Russia's TSPU or Iran's DPI to match and drop. MTProto proxies exist to bypass these filters, and they do it with three layers: obfuscation, random padding, and FakeTLS. Here’s how each works and why DPI can’t keep up.
MTProto Protocol Basics (Transport Layer)
Telegram's transport layer is not vanilla TLS. It uses a custom framing protocol over TCP with its own built-in encryption. The first four bytes of a connection are either:
0xEEEEEEEE for plain (deprecated)
0xEFEFEFEF for abridged (no checksum)
