A Media Access Control (MAC) address is essentially your computers hardware address. Much like an IP address can show where your computer is located in the world, a MAC address can be used to determine the hardware manufacturer. Spoofing basically means to trick or deceive. What you are doing when you spoof your MAC address is making people believe it has a different address than it actually does.
More information on the background and history of MAC addresses can be viewed here.
In the following examples I will show how to spoof a MAC address for Windows and Linux.
The first step is to open up the registry editor. This can be done by clicking start > run and then typing “regedit”. Once in regedit navigate to the following key:
Scroll through the subset of this folder until you see a value that matches your network adapter stored in DriverDesc:
You should find a value called NetworkAddress. Right click on this value and select modify. Enter a 12 digit number with no spaces. This can be whatever you would like it to be. You should enter it like this:
Sometimes the NetworkAddress value does not appear in the current location. You can simply add it yourself by right clicking, and selecting New > String Value. Enter NetworkAddress as the name and then enter your 12 digit number.
After this go to Control Panel > Network Connections and disable and re-enable your network card.
It is much simpler to spoof your MAC address on Linux. Open a terminal window and type the following.
infconfig eth0 down ifconfig eth0 hw ether 11:22:33:44:55:66 ifconfig eth0 up
Substitute eth0 with whichever interface you are trying to spoof the MAC address on. Normally wireless cards are wlan0, but to find out for sure type ifconfig and verify for yourself.