MacOS has a lot of BSDisms under the hood. For example it still comes with OpenBSD's pf firewall. You can access it with the pfctl command and it's documented i

MacOS has a lot of BSDisms under the hood. For example it still comes with OpenBSD's pf firewall. You can access it with the pfctl command and it's documented in the man pages. Note that this is not the application firewall that can be activated in system preferences. It's entirely separate and only accessible from the console or third party software like icefloor.