Here goes the steps for disabling inbound MySQL connections to a linux server.
♦ Login to the server as root
♦ open the file /etc/my.cnf
♦ add the directive skip-networking
♦ save and quit from the file.
Now you may need to disable the port 3306 in TCP_IN section in firewall(if firewall enabled).
Make sure that the server is not listening to the inbound MySQL connections by telnet.
telnet x.x.x.x 3306