Activate the Mac OS X 10.6 (Snow Leopard) Firewall

To activate the firewall in Mac OS X 10.6 (Snow Leopard), follow these steps:

1. From the Apple menu, click System Preferences.
2. In the System Preferences window, click the Security icon in the top row. This icon is circled in white in the following graphic:
   
   
   

3. In the Security window that appears, click the Firewall tab.
4. If not already enabled, click the Start button to turn on the firewall.
5. The window should now look similar to the following:
   
   
   

6. Click the Advanced button in the lower-right corner of the window.
7. If a check mark is not already present, click in the checkbox in front of Block all incoming connections.
   
   NOTE
   A check mark should simultaneously appear in the checkbox in front of Enable stealth mode near the bottom of the window.

8. The window should now look similar to the following:
   

9. Click OK.
10. Close the Security window.