How to isolate apps from the internet?

Question

Can I completely isolate apps on mac from the internet, without installing any additional software ?

I need a sort of firewall to isolate them thanks

Answer 1

No, you can't without additional software. The only solution would be to cut the Internet connexion of your computer.

You can block incoming connexions though, using the standard Mac OS X Firewall (accessible in the Security & Privacy panel of the System Preferences). When activated, when an application wants to start listening on a certain port, you are prompted to allow or deny the listening.

With additional software, you can use the excellent Little Snitch application that allows blocking outgoing connexions as well.