I recently started receiving excessive 404 errors from a server in Hungary attempting to access random folders in my root url. The source url was 37.17.172.122 which was generating these 404 errors.
I setup in security/Login settings/Login IP Filters to deny is ip address. but I kept receiving 404 errors from this ip until I did a server 'Clear Cache' & 'Restart application'.

Just thought others should know.

Any other suggestions?