Direct connection is a Minecraft security plugin which protects against people connecting to a malicious port which you can setup through a few simple commands. This can help stop cracked players from logging in using your Minecraft username from an offline server.
Examples:
Code (Text):
Messages:
KickMessage: '&8[&cDirectConnection&8] &7All connections from this port have been
denied. Please connect via &a{IP}'
Settings:
Disallowed Ports: PleaseChangeThis
IP: example.com