FixProxyJoin — is a simple plugin that protects the entrance to the lobby or to any other server connected to Bungeecord. An attacker will not be able to log into your server from his fake bungee cord if you install this plugin on all Bungeecord servers.
When a player enters the server, the IP address from which he entered is checked, if the address does not match your proxy server, then the player cannot connect.

Installation:
Place the plugin in the /plugins folder with regular servers connected by a bungee cord.
Write a command on the server or in the console /fpj address: port, where the address is the ip address of your Bungeecord server and its port, respectively.

Commands:

• /fpj <ip: port> » add adress
• /fpjdel <ip: port> » delete adress

Permissions:

• fpj.enter » add adress
• fpj.del » delete adress