Want to assume a new identity on a network? This function will give you a random (non-multicast) MAC address.

random-mac.zsh

function random-mac() {
  local interface="${1:-en0}"
  local old_addr=`ifconfig $interface |grep ether|awk '{print $2}'`
  local new_addr=`ruby -e "puts ('%02x' % ((rand 64)*4|2))+(0..4).inject('') {|s,x| s + ':%02x' %(rand 256)}"`
  `sudo ifconfig $interface ether $new_addr`
  if [ $? -eq 0 ]; then
    echo "Switched mac address on $interface to $new_addr from $old_addr"
  else
    echo "FAILED TO SWITCH MAC ADDRRESS ON $interface"
  fi
}