OS X: About the application firewall - Apple Support

OS X: About the application firewall - Apple Support

Use these steps to enable the application firewall:

1. Choose System Preferences from the Apple menu.
2. Click Security or Security & Privacy.
3. Click the Firewall tab.
4. Unlock the pane by clicking the lock in the lower-left corner and enter the administrator username and password.
5. Click "Turn On Firewall" or "Start" to enable the firewall.
6. Click Advanced to customize the firewall configuration.

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