This process is also known as spoofing.
# generating a random mac: openssl rand -hex 6 | sed 's/\(..\)/\1:/g; s/.$//' # ↑ although this doesn't take care of bit 0 and 1 of byte 0 which should be 0. # ( http://en.wikipedia.org/wiki/MAC_address#Address_details ) # changing the MAC address: sudo ifconfig en0 ether xx:xx:xx:xx:xx:xx