Believe it or not, the number of MySQL servers here in Asia that are still infected by various virusses is on the order of 10,000 or so. Even though one's MySQL server may not be vulnerable, dealing with all the scans from infected machines adds a considerable load to any MySQL server simply by having to continually refuse connection attempts. Although one can easily add a ISPConfig firewall entry specifically for MySQL, it might be a good idea to add an entry for it automatically during the initial installation of ISPConfig. I manually added an entry, in Management > Services > Firewall > Firewall Rule Add, and then immediately set "Active" to "no", thereby closing the port but not having run into problems in the past with MySQL being open, I might not have thought to do that.
The mysql port is closed in ispconfig by default. A service that is not listed there is closed, so adding a service and setting active to no is the same then not having this service listed there.
