[saulr]

I believe newer Valve multiplayer games (e.g. Dota, CSGO) use Steam Networking instead of the game sending UDP itself. Packets sent with Steam Networking are encrypted[0].

Before CSGO moved to Steam Networking, the game itself encrypted the packets. I can't remember exactly when this was introduced, but it's still in place - see https://github.com/alliedmodders/hl2sdk/blob/acf932ae06b64b7...

[0] https://partner.steamgames.com/doc/features/multiplayer/netw...