The MAC Address

The MAC (Media Access Control) address or hardware address is burned in (hence is also called burned-in address) on every Ethernet Network Interface Card or NIC and is unique on every card. It is used by the Ethernet protocol for addressing in the Layer 2 OSI model. It is divided into two parts. The Organizational Unique Identifier (OUI), which is the first 6 HEX digits assigned by IEEE and the second 6 is assigned by the vendors themeselves to uniquely represent the NIC within the OUI. Every ethernet device will have this in its system.

Finding the MAC address or Physical address of your PC is fairly easy. Just go to the command prompt or DOS prompt and type "ipconfig /all" without the quotes.

You can also learn the MAC address of those PCs or devices which your PC recently had communication with by looking at the arp cache table using the arp -a or arp -g command in the command prompt.

Though it is not recommended, there are some ways to change the MAC address of your PC through software methods. It is important to take note that changing the MAC address can adversely affect the stability of your network. One long method is via the windows registry. You can refer to this site for the proper procedure. Or you can change it through the network card properties. But if you are not comfortable changing it, you can always try MAC spoofing such as SMAC. The SMAC software will try to hide your real MAC address from your network.

Why does anyone bother changing the MAC address anyway? Here are some of the reasons why:

1) for personal privacy since some companies do track users via their MAC addresses. However it is also a technique being used by hackers to hide themselves or to spoof other machines.
2) for performing security vulnerability and penetration testing.
3) to build high-availability netowrk solutions such as devices that run multiport NICs

If you are curious enough to find the OUIs assigned to some companies such as Cisco you can try this link: IEEE OUI and Company_ID Assignments. Just type the company name in the search box.