Modify MAC address

Modify MAC address under Windows

Under Windows XP, the MAC address can be modified in the Ethernet adapter's Properties menu, in the Advanced tab, as "MAC Address", "Locally Administered Address", "Ethernet Address" or "Network Address". The exact name depends on the Ethernet driver used.
However, not all drivers support modify MAC address in this way.

A better way to modify MAC address - requiring Administrative User Rights - is to pass over the System Registry Keys under HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlClass{4D36E972-E325-11CE-BFC1-08002BE10318}. Here settings for each network interface can be found. The contents of the string value called 'NetworkAddress' will be used to set the MAC address of the adapter when it is enabled.

Note: to check your MAC address easily on a Windows XP box, go to Run, type CMD, then type "ipconfig /all" without quotation in the command prompt. The number under physical address is the MAC address. If multiple IP are displayed, you should look under the label "Ethernet adapter x", where x is the name of your connection (which is Local Area Connection by default).

Modify MAC address under MAC OS X

Under Mac OS X, the MAC address can be altered in a fashion similar to the Linux and FreeBSD methods:
sudo ifconfig en0 lladdr 00:01:02:03:04:05
or
sudo ifconfig en0 ether 00:01:02:03:04:05

This must be done as the superuser and only works for the computer's ethernet card.