If I understand correctly, by default Asterisk uses port 5060 when dealing with SIP communications, and that’s why this port should be opened/redirected in IPTables/Router configuration. But my question is this: if my Asterisk only deals with Outbound calls (that is, I only want to make calls, but not to receive any call), is it mandatory (or at least, recommendable) to keep that port opened? I mean, since Asterisk is the one who will always initiate calls from inside my network/computer, do I really need to allow access to that port from the outside?
I’m asking this because I’m pretty tired of finding hackers trying to register into my system using that port, and although Fail2Ban + Strong passwords have manage the situation quite well, I would prefer to close that port if possible.
I have performed a basic test without opening that port and calls seem to be OK, but I don’t know if there will be any side effect when using this configuration in a real environment (calls dropped, bad sound…).