iptables -I INPUT -p tcp --dport 3306 -j DROP
/etc/init.d/iptables save

/*
After you've run the above command, you can undo it by editing /etc/sysconfig/iptables and running /etc/init.d/iptables restart
*/

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The command you need to close the mysql port 3306 from external access.  You need to use the 2 lines in the snippet below once you have connected to the server via SSH.

Close the mysql port (3306) from external access.

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