For search current MAC address:
ifconfig en0 | grep ether
For change MAC address:
sudo ifconfig en0 ether aa:bb:cc:dd:ee:ff(New MAC)
For Disable LAN:
sudo ifconfig en0 down
For Enable LAN :
sudo ifconfig en0 up
Other procedure:
sudo ifconfig en0 ether 00:00:00:00:00:00 ,where en0 is the network interface you wish to change the MAC address of, and 00:00:00:00:00:00 is the target MAC address. This code cannot be used in Leopard, but it turns out the solution is extremely simple, and just as straightforward. Again in Terminal, just type: sudo ifconfig en0 lladdr 00:00:00:00:00:00
