The macOS Application Firewall controls which applications are allowed to accept incoming network connections. It is different from a traditional port-based firewall.

Enable the Firewall

Go to System Settings > Network > Firewall and toggle it on.

Enable Stealth Mode

Click Options and enable Enable stealth mode to prevent your Mac from responding to ping requests.

Manage App Permissions

Under Options, you can allow or block specific applications from accepting incoming connections.

sudo /usr/libexec/ApplicationFirewall/socketfilterfw --getglobalstate