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Article by Amit Chawla

 

Although physical MAC addresses are permanent by design, several mechanisms allow modification, or “spoofing”, of the MAC address that is reported by the operating system. When connecting to a Wi-Fi hotspot, or to ensure interoperability, this can be useful for privacy reasons. If the user changes their network card or intends to install a router, the service won’t work anymore because some ISPs bind their service to a specific MAC address. To solve the problem change the MAC address of the new interface. However, this method will not work, if the Internet service provider is able to detect that a MAC address is changed and prohibits spoofed MAC addresses. Similarly, some of the Security software that can be downloaded on the limited number of machines is bound to a specific MAC address.

 

With most of the operating systems and drivers installed, the MAC address will be reverted to the physically value stored in the card after a reboot as software-based changes to the MAC address simply modify operating system configuration data and are not permanent.

 

On the other hand, the permanent change to the MAC Address is the hardware-based change because it erases the MAC address physically stored in the card’s EEPROM and overwrites it with a desired MAC address. Want a hardware-based modification which is tricky, however, as it requires an EEPROM Programmer (hardware) and the user to operate desoldering equipment.

 

It can be unwise to rely on this as a single method of authentication, as a MAC address can be changed. IEEE 802.1x is an emerging standard better suited to authenticating devices at a low level.

 

In order to change MAC Address under Windows XP, simply follow the steps below

Go to the Properties menu of the Ethernet adapter, in the Advanced tab, as “MAC Address”, “Locally Administered Address”, “Ethernet Address”, “Physical Address” or “Network Address”. The exact name depends on the Ethernet driver used; not all drivers’ support changing the MAC address in this way.

 

However, to pass over the System Registry Keys is a better solution than requiring Administrative User Rights

 

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002BE10318}.

 

Here you can find the settings for each network interface. To set the MAC address of the adapter when next it is enabled will be the contents of the string value called ‘NetworkAddress’.

 

The freely available command line utility devcon[7] from Microsoft can be used for resetting the adapter in script or from the adapters context menu in the Network Connections control panel applet.

 

Note: In order to check the MAC address under Windows NT4, Windows 2000 or Windows XP, try the steps below:

Click on the “Start” button.

Choose “Run”, type “CMD” (without quotes) and click on the <OK> button.

Then type “ipconfig /all” (without quotes) in the Command Prompt window that appears and press the Enter key from your keyboard.

 

 MAC address is the number under physical address. If displayed multiple IP, then you have a look under the label “Ethernet adapter x”, where x is the name of your connection (which is Local Area Connection by default).

 

The ‘getmac’ command to retrieve the MAC addresses from installed hardware connected to your machine is also supported by Windows XP Pro. Click “Start”, choose “Run…”, type COMMAND and click OK, then type getmac /v in the Command Prompt window. getmac /? provides help on the various command options.