Can someone explain from a technical standpoint how they can block OpenVPN running on port 443? my admittedly limited understanding is that port 443 is the common port for https. If they blocked that port wouldn’t that mean that they would be blocking nearly the entire internet?
I don’t know what they actually do but one possibly is to look for (absence of) the TLS handshake. Or maybe they simply infect all devices on the Chinese market with MITM certificates to be able to decrypt all TLS encrypted traffic. Should be easy to force companies to do that in such a country.
The port isn’t their focus, they’re looking at the protocol that is being used, regardless of the port. The protocol is still visible when not doing deep packet inspection. That’s why there suggesting a socks proxy for Russian citizens, because that uses HTTPS to tunnel traffic, so it wouldn’t be caught up in protocol analysis.
can you maybe link some ressources on how the protocol used can be detected? i did not know about this and would like to read into it some more :)
From my understanding, they are most likely just blocking the defualt port of wireguard / openvpn and IPs associated with the VPN servers of VPN providers they dont like.
If they wanted to block VPN traffic over 443 to any IP, they would have to do deep packet inspection, which I would imagine is infeasible for Russia.
Supposedly, the Chinese great firewall does use deep packet inspection, so it is possible to do this at the country level.
