Every network interface device has a unique identifier called a MAC
address. The MAC address comes in the form of xx-xx-xx-xx-xx-xx or xx:xx:xx:xx:xx:xx.
It is useful for several reasons, not the least of which is security. Many routers
allow you to filter out access according to MAC address, meaning you can disallow
certain MAC addresses, or allow certain MAC addresses.
Finding your MAC address
In Windows XP the MAC address is shown in the connection properties of the
interface card. In the Control Panel, open Network Connections, then right-
click the desired connection, then click Properties. Under the support tab
there is a button labeled Details. In the window that appears, the MAC address
is called "Physical Address."
After becoming root, type in "ifconfig -a". Find the desired device name. The
MAC address is listed as HWaddr.
Open the Apple Menu and select Conrol Panels. Open the TCP/IP panel. Under the
Edit Menu, click on User Mode and change it to Advanced. Click the Info button.
The Hardware Address is the MAC Address of the network device.
From the Dock, open System Preferences. Select the Network Pane. In the TCP/IP
Tab, the Ethernet Address is the MAC address of the selected connection.
Changing your MAC Address
It is possible to change your MAC address, though not necessarily recommended.
The practice of changing your MAC address is called "IP Spoofing," and is useful
to both legitmate users, and also those with malicious intent. Changing your MAC
address can either allow or disallow you access to a filtered network. When doing
so, you should verify both the network owner's knowledge of your actions, and also
When logged in with Administrative rights, use the Run tool to open RegEdit. Browse
to the registry entry at
The string value called NetworkAddress will be set to your current MAC address. You
must reset the adapter for the new value to take effect.
In a console, log in as root, then use the ifconfig command to change the address
using the following syntax: ifconfig eth0 hw ether xx:xx:xx:xx:xx:xx
In the console, use "sudo ifconfig" using the following syntax:
sudo ifconfig en0 lladdr xx:xx:xx:xx:xx:xx