is disabling “set date and time automatically” in Software Preferences enough to ensure that ntpd is not running?
Yes.
Here is the way to insure yourself of this.
Open a Termonal or xterm window.
Run the following command:
ps ax | grep ntp
and notice that you have an ntpd process running.
Open System Preferences and
turn off Set date and time automatically:
Check with the ps command above that you don't have any ntpd process running.
Don't remove the `ntpd` binary, this is not necessary and would deprive you of the chance to take advantage of a fix from Apple :).
> In doubt I might use these instructions to limit the scope
No.
This receipe will live you with a running ntpd and hence exposed to an attack.