Select the “MAC Filtering” tab. Choose one of the following: “Deny access for the listed MAC addresses” if you wish to block access to specific MAC Addresses. “Allow access for ONLY the listed MAC addresses” if you wish to allow access to specific MAC Addresses.
Tip • If you don't feel comfortable using Terminal to make changes, consider using one of the free firewall programs like Little Snitch, WaterRoof or NoobProof (links in Resources). These applications provide a user-friendly interface that allows you to easily disable outgoing applications for specific applications or all network activity. Little Snitch works well if you're an advanced user who wants to monitor all incoming and outgoing connections in real-time. WaterRoof provides options if you want to keep the OS X firewall active and still use advanced rules to configure dynamic rules, NAT and port-forwarding, bandwidth managers and other options. NoobProof provides a user-friendly approach without many of the advanced options available in WaterRoof.