How to Setup a Password to Play on your Server
Setting up a password is ideal for offline mode/cracked servers. This prevents hackers from spoofing admin accounts and causing mass destruction to your server. It also prevents hackers from spoofing other players and stealing their items.
We recommend the plugin OpeNLogin. It is a free & secure authentication plugin that supports Minecraft [1.7.X - 1.17.X]
https://www.spigotmc.org/resources/57272/
You must be running Spigot or a fork of Spigot to use this plugin.
Setup Guide:
Stop the server if it's running.
Download the OpenLogin.jar file and place it in the plugins folder using the File Manager or SFTP Client.
Start the server.
Join your server and open the Chat window.
We recommend selecting nLogin for extra security.
Once the server restarts, players will now be required to register a password. Every time that player joins the server, they will be required to input their registered password to play.