So, you looked in /var/log/mysql/error.log and you found something like:
Hostname ‘visit.domains.com’ does not resolve to ‘18.104.22.168’.
(that domain and IP are made-up)
But you’re running the CSF/LFD firewall and you have port 3306 blocked and bind-address is 127.0.0.1 in your [mysqld]. What is going on?
You may have opened ports 30000:50000 in CSF for passive FTP a long time ago and forgotten about it. And then an update to MySQL came along and made this a default:
X Plugin ready for connections. Socket: '/var/run/mysqld/mysqlx.sock' bind-address: '::' port: 33060
Notice that 33060 is within 30000:50000. So you had a port range open, and a server came along and started listening on a port within that range. Now people are trying to connect to your MySQL server using the X plugin.
Now you know.