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 Windows XP/2000 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." Linux After becoming root, type in "ifconfig -a". Find the desired device name. The MAC address is listed as HWaddr. MacOS (Pre-OSX) Open the Apple Menu and select Control 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. Mac OSX 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 legitimate 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 your intentions. Windows XP/2000 When logged in with Administrative rights, use the Run tool to open RegEdit. Browse to the registry entry at HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002BE10318} 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. Linux 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 Mac OSX In the console, use "sudo ifconfig" using the following syntax: sudo ifconfig en0 lladdr xx:xx:xx:xx:xx:xx

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