A MAC address is a unique 12 digit 48 bit number assigned to every network adapter. They are often used to uniquely identify a MAC on a LAN. A MAC address is organized like this:
XX-XX-XX-ZZ-ZZ-ZZ
If you are using a network adapter and wish to see your own MAC address, you can use winipcfg for win9x systems
ipconfig for win2000 and winNT
ifconfig -a for linux
And if you are using a macintosh, then you must do one of two things to find out your MAC address. Go into the TCP/IP control panel, then if you are using MacTCP click the ethernet icon or if you are using open transport then click info or user mode/advanced

The first 3 sets of numbers, or the first 6 numbers indicate the manufacturer of the network adapter, and the last 3 sets of numbers or the last 6 numbers indicate the unique number that the manufacturer gave to that specific network adapter. So, right there, you can see that an obvious security issue exists. Which is just one more reason to obtain a good firewall and to block sites and other users on the internet from seeing your MAC address. Also, if you use Win2k or Linux you may be able to change what others see as your MAC address. To find instructions on this plz see my other tut on MACs at

http://www.antionline.com/showthread...hreadid=231058

MACs work at the data link layer in the OSI model, layer 2. Many IP networks maintain a list of the IP addresses for a device and the MAC addresses. That is what is where ARP comes in, this list, is the ARP table or ARP cache, (Address Resolution Protocol).

I have included a list of MAC manufacturers and what their MAC prefix is, so that if you do not know the maker of your network adapter, consulting the list will porbably tell you.

And one more thing, many broadband providers use DHCP to assign IPs to their users, so changing MAC addresses or tampering with them could cause you to be cut off from your broadband provider.