Block a client from connecting to MySQL if too many errors
You can block a client from connecting to MySQL if they introduced too many errors, e.g. sending incorrect password for authentication, insufficient privileges when connecting to a database etc.
To set the number of maximum allowed error, edit the MySQL configurations, e.g. /etc/my.cnf
.. max_connect_errors=100 ..
So if a client exceeded this value, they will be blocked from connecting to the server.
Don't forget to restart MySQL to take effect.
# /sbin/service mysqld restart