Technology

Attached below is a Wireshark trace I obtained by sniffing my own network traffic.

I want to draw your attention to this part in particular:

Underneath "User Datagram Protocol", you can see the words "OpenVPN Protocol". So anyone who sniffs my traffic on the wire can see exactly the same thing that I can. While they can't read the contents of the payload, they can tell that it's OpenVPN traffic because the headers are not encrypted. So if a router wanted to block OpenVPN traffic, all they would have to do is drop this packet. It's a similar story for Wireguard packets. An attacker can read the unencrypted headers and learn

• The size of the transmission
• The source and destination IP addresses by reading the IP header
• The source and destination ports numbers by reading the TCP or UDP headers
• The underlying layers, up until the point it hits an encrypted protocol (such as OpenVPN, TLS, or SSH)

They're going to know it's VPN fairly easily because it's fairly obvious what you're doing when all or most of your traffic is encrypted and is directed at one or two addresses. Even more obvious if those one or two addresses happen to belong to known VPN or VPS providers or something.