Information
A firewall is a piece of software that blocks unwanted incoming connections to a system. Apple has posted general documentation about the application firewall:
Rationale:
A firewall minimizes the threat of unauthorized users gaining access to your system while connected to a network or the Internet.
Impact:
The firewall may block legitimate traffic. Applications that are unsigned will require special handling.
Solution
Graphical Method:
Perform the following steps to turn the firewall on:
Open System Settings
Select Network
Select Firewall
Set Firewall to enabled
Terminal Method:
Run the following command to enable the firewall:
$ /usr/bin/sudo /usr/bin/defaults write /Library/Preferences/com.apple.alf globalstate -int <value>
For the <value>, use either 1, specific services, or 2, essential services only.
Profile Method:
Create or edit a configuration profile with the following information:
The PayloadType string is com.apple.security.firewall
The key to include is EnableFirewall
The key must be set to <true/>