Details
A firewall is a piece of software that blocks unwanted incoming connections to a system. Apple has posted general documentation about the application firewall.
http://support.apple.com/en-us/HT201642
Rationale:
A firewall minimizes the threat of unauthorized users from 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
Perform the following to implement the prescribed state:
Open System Preferences
Select Security & Privacy
Select Firewall
Select Turn On Firewall
Alternatively:
Run the following command in Terminal:
defaults write /Library/Preferences/com.apple.alf globalstate – int
Where
1 = on for specific services
2 = on for essential services
Additional Information:
http://docs.info.apple.com/article.html?artnum=306938
Supportive Information
The following resource is also helpful.
This security hardening control applies to the following category of controls within NIST 800-53: System and Communications Protection.This control applies to the following type of system Unix.