You can click on the "Server Administration" link on the left "Management" menu from in the Centova Cast control panel;
http://servername:port and log in
username : admin
Admin Password : (available in the stream panel, same password as your control panel password).
at the top of the page you will see the main menu, click on “ban list” from that menu. Now just enter the IP address and click on “Ban Single Host” or you can enter the subnet and then click on “Ban Whole Subnet”.