Using ipfw you can filter network traffic by MAC address. For example if you want to block traffic from/to some MAC address you can use the following commands:
ipfw add deny ip from any to any MAC 00:07:E9:AD:E8:26 any
ipfw add deny ip from any to any MAC any 00:07:E9:AD:E8:26
Using these commands we block all traffic for the computer with MAC address 00:07:E9:AD:E8:26.
But this blocking will not work if net.link.ether.ipfw variable is set to 0. So you should also do the following command: