The quickest way to spoof your MAC address is to download SpoofMAC directly from GitHub.
What is SpoofMAC?
Something I’ve needed to do from time to time is spoof my computer’s MAC address. This is useful for debugging network issues or temporarily getting onto the Stanford Wi-Fi network when my physical MAC address changes, such as when Apple replaced my logic board (motherboard).
For the uninitiated, a Media Access Control address (MAC address) is “a unique identifier assigned to network interfaces for communications on the physical network segment”. You can read more on Wikipedia.
Despite the fact that all network devices (laptops, iPhones, routers, etc.) have physical MAC addresses burned into the hardware, you can actually change (or spoof) your MAC address completely in software, and other network devices will only see your spoofed address.
Other Solutions Sucked
I was disappointed with the Mac OS X offering in this area. None of the existing stuff worked well. The biggest annoyance with most of the solutions I found was that the Wi-Fi card (Airport) needs to be manually disassociated from any connected networks, in order for the change to be applied correctly. Doing this manually every time is annoying.
Also, OS X doesn’t let you permanently change your MAC address. Every time you restart your computer, your address gets reset back to whatever it was before. Fortunately, SpoofMAC contains the necessary files for setting this script to run at startup time, so your computer will always have the MAC address you want.
So, I made a Python script that lets you change your MAC address in one command. Check it out and download it from Github. Improvements welcome!
Let me know in the comments if you find this useful.
Update (March 18, 2013)
Since uploading this to GitHub, SpoofMAC has received many useful code contributions. It now supports Windows and Linux, MAC address randomization, and more. I <3 open source!
(If you liked this, you might like How To Set Up Your Linode For Maximum Awesomeness.)