Setting Up a Firewall: Mac OS X 10.6.x (Snow Leopard)

Learn how to set up the Mac OS 10.6.x firewall to protect your computer against malicious activity.

Note: This basic firewall closes off unused network service ports, but lets you create exceptions for specific programs running on your computer. To check your version of OS X, open the Apple menu (the blue apple icon in the upper left corner of the screen), and selectAbout This Mac.

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1. Open System Preferences.

• Open the Apple menu, and select System Preferences…
• Click the Security icon in the Personal area of the window, or open the View menu at the top of the screen, and selectSecurity.

2. Activate the firewall.

• Click the Firewall tab.
  • Note: If the Start button is gray and you can’t click it, click the lock icon at the bottom of the window, and enter your adminstrator password when prompted.
• Click the Start button.
• Click the Advanced button.
• Select the desired firewall configuration.
• Click OK.
• Close the Security pane to save your selections.

3. Create program exceptions.

• Click the Firewall tab in the Security pane.
• Click the Advanced button.
• Click the + symbol.
• Find the program that you'd like to add as an exception.
• Click the Add button.
• Repeat the above steps for each program you'd like to add to the exceptions list.
• Set whether to Allow incoming connections or Block incoming connections for the programs in your list by clicking the up or down arrows to the far right of the program name, then selecting the appropriate option.
• Click OK.
• Close the Security pane saving your selections.

Note: UCSD does not officially recommend any exceptions; any university programs will not be affected. However, in the example below, George Bluefin has added iTunes as an exception. If he did not have iTunes enabled in his firewall exceptions list (which allows incoming connections), people wouldn't be able to connect or listen to his shared music when his firewall is on.