Searching for the keywords "accept incoming connections" in ran into questions asking how to stop the message box keeping to pop up. I would rather like to know, quite generally, why application require incoming connections at all.

How can a normal user decide to accept incoming connections or not? After all, firewalls are a security feature.

For the question https://stackoverflow.com/questions/4499578/do-i-need-to-allow-the-application-stoned-to-accept-incoming-networking-connec , one answer given was:

No, definitely don't allow any app to accept connections if you're unsure.

I don't consider myself a normal user because I have at least some admin knowledge. But still I struggle with that problem. There are several reasons for asking:

  • these messages pop up from time to time, seemingly without any cause

  • it doesn't seem to make any difference if I accept or not; the applications keeps working

  • as far as I understand the inner workings of firewalls, applications on my computer initiate communication to the world themselves, and only then the firewall allows communication back to my application. With this view, incoming connections refer not internally initiated communication (right...?). If this is true, I wonder how some external party knows that the application is running on my computer.

  • after accepting (or not), the app appears in the firewall rules. Why do I see an exception rule for not accepting, instead of only those apps for which I accepted. Seems not to make any sense.

A few minutes ago a got the message to accept incoming connections for timed (time synchronisation daemon, according to man pages). I have never seen this request before; shall I accept ...?


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