In OS X 10.6.5, the following dialogue popped up:
What is this application? What does it do?
EDIT (to increase googlability): OS X firewall: Do you want the application "master" to accept incoming network connections?
"master" is part of the Postfix mail server system that comes installed by default on every Mac. It is usually disabled, I can't say why it might be activated.
I use OSX 10.8 with the server app, and this message appeared to me after: - I activated mail notifications about network modification, etc. of my server - I installed 10.8.1
So, I think it's the reason why the
postfix mail server is started & why the message has appeared (it's my first reboot since my 10.8 upgrade 3 weeks ago)
That looks fishy to me. Open up Activity Monitor, look for a process named "master," and then find the location of the executable by running
$ ps -ax|grep the_PID_from_activity_monitor in Terminal.
That might give some insight.