Probably not hacked, and you don't need to do anything. It is a server side error that is getting displayed in your browser......
By default, mysqld blocks a host after 10 connection errors. You can adjust the value by starting the server like this: shell> mysqld_safe --max_connect_errors=10000 &
If you get this error message for a given host, you should first verify that there isn't anything wrong with TCP/IP connections from that host. If you are having network problems, it does you no good to increase the value of the max_connect_errors
variable.