[alex1]

FWIW, here's what I got on an Ubuntu 12.04.3 server running on my LAN. It looks like we should be fine with the defaults on Ubuntu at least. (Obviously always a good idea to use ufw/iptables to block everything you don't need exposed so you don't have to worry about stuff like this).

Before installing ntp (from another host on my LAN):

  $ ntpdc -n -c monlist 192.168.1.50
  ntpdc: read: Connection refused

After installing ntp (from another host on my LAN):

  $ ntpdc -n -c monlist 192.168.1.50
  192.168.1.50: timed out, nothing received
  ***Request timed out

After installing ntp (from the server itself):

  $ ntpdc -n -c monlist localhost
  remote address          port local address      count m ver rstr avgint  lstint
  ===============================================================================
  91.189.94.4              123 192.168.1.50         1 4 4    1d0     54      54
  ...

[voltagex_]

Thanks, I should have checked this.