ntp server - changing port to non-standard? possible?

Howdy -- it's rare that one needs to provide NTP to the general public. If you're concerned about it listening for requests, you could always use a firewall to block access to the port.

I haven't tried changing the port on NTP before though, I'm unfortunately not sure what's involved with that... you can get info on how to do that by reviewing the ntp.conf manpage though. The firewall option is likely the simplest option since it sounds like you're running one.