In computing, Virtual Network Computing (VNC) is a graphical desktop-sharing system that uses the Remote Frame Buffer protocol (RFB) to remotely control another computer. It transmits the keyboard and mouse events from one computer to another, relaying the graphical-screen updates back in the other direction, over a network. From wikipedia.
VNC usually uses ports 5800 or 5801 or 5900 or 5901.
PORT STATE SERVICE5900/tcp open vnc
nmap -sV --script vnc-info,realvnc-auth-bypass,vnc-title -p <PORT> <IP>msf> use auxiliary/scanner/vnc/vnc_none_auth
vncviewer [-passwd passwd.txt] <IP>::5901
Default password is stored in: ~/.vnc/passwd
If you have the VNC password and it looks encrypted (a bunch of bytes). It is probably ciphered with 3des. You can get the clear text password using https://github.com/jeroennijhof/vncpwd
makevncpwd <vnc password file>
You can do this because the password used inside 3des to encrypt the plan-text VNC passwords was reversed years ago.