Oh okay. Now I see, I misinterpreted what it did there.
1, 2) I thought it was a way to force the FTP server not to respond anything if the host mask was not allowed, i.e. not reveal that there's an FTP server on the other end of that port. I probably don't know enough about the FTP protocol to understand if that would even work.
If there's a way to do that at least I would be very much interested.
4) I see.
5) Yeah I understood that. Just thought that 3 was a good number, at least to test it. With fewer you could have it triggered with a port scan (ascending/descending) if they're somewhat close, right? And I don't see the point for more than 3.
I'm only using ioFTPD for a regular home FTP, but with more options and security. So I would like to set it up very secure since it's kind of an hobby. So most my users don't have any dynamic DNS. As I said, I thought it was a way to force the server not to reveal itself if the host wasn't allowed.
Thanks a lot for responding fast and thoroughly.