Is this secure?

Hello,

I have a Spigot server with BungeeCord. Spigot is in offline-mode, BungeeCord is in online-mode.

spigot.yml: bungeecord: true
config.yml: ip_forward: true

Now I have tried to connect directly to the server, it didn't work and it shouldn't work. I can just connect to the server over the proxy-server. Seems good, but is this really secure? I actually don't use a firewall or a plugin that blocks a direct connect to the server.