Computer MAC addresses explained

Any hardware with a communications network interface card (NIC) will have been assigned by the manufacturer of the card a unique Media Access Control (MAC) address embedded on the network card, this address includes the manufacturer identification number, the make and model of the device could be embedded too. A MAC address takes the viewable form of six groups grouped in blocks of two hexadecimal digits (composed of numbers from 0 through 9 and letters from A up to F) separated by hyphens or colons.

Example MAC addresses: 00-B0-D0-86-BB-F7, 09:00:07:A9:B2:EB, D1-AD-04-EF-C1-02

A network interface card MAC address does not contain user information and it is not visible on the Internet, it remains behind the router, a router will use a device MAC address to identify a local computer, the router will be able to see and log the device MAC address when connected to, if you are using a public wireless access point for example, the access point will log your network card MAC address, time and date.

A network administrator could use this information to link your machine, i.e. laptop, mobile device, etc, with a particular Internet session, in order to do that you would have to lose control of the device and allow someone to examine it, using a VPN on a Wi-fi connection will not hide your MAC address.

Note: A computer MAC address is not related to Apple Macintosh computers, it is related to network cards.

How to find out a computer MAC address 

Windows MAC address: Go to the command line (Run>cmd) and type ipconfig /all you will see a line that says “Physical address”, that is your network card burned-in address, aka MAC address, if  you have a wireless router you will see more than one physical address, one belongs to the ethernet wired connection and the other to the wireless connection.

Apple Macintosh MAC address: Go to System Preferences>Network Icon>Show (select Built-in Ethernet)>Ethernet Card, the MAC address is listed next to Ethernet ID:, to determine the MAC address of a Wi-fi card select Show: Airport>Airport the address is listed next to Airport ID:

Linux MAC address: Become root at the command line (typing su or root) and type ifconfig -a the MAC address will be listed next to HWaddr on the first line, or type /sbin/ifconfig | grep HWaddr

FreeBSD MAC address: Type dmefg to see display MAC address or grep eth0 /var/log/dmesg or type ifconfig and look for the ether line, the MAC address will be written next to that.

Note: A hard coded MAC address is meant to be unique in the world, there can only be one NIC card with that number, if  you spoof a network MAC address and it coincides with that of another device in the same local network there could be serious networking problems, or data could be forwarded to both devices, the consequences will depend on how the switch handles it.

How do I change my MAC address? 

To physically change a network card MAC address it is necessary to remove the NIC card flash chip, re-programming it with new MAC address and putting it back on the card, changing your device network card will also change the hard coded MAC address, the easiest and quickest way to change a MAC address is by using special MAC address changing software:

DynaMAC: Freeware application to view and change any computer MAC address, including wireless cards, the user can specify the MAC address that should be used, the old address can easily be reset to the original one with a single click.

After downloading DynaMac choose custom installation to stop your homepage and default search engine from being changed (Ad-aware).

DynMAC free MAC address changer

DynMAC free MAC address changer

Technitium Tmac: Highly configurable MAC address changer, it provides complete information on all of your network cards MAC addresses, you can select a random MAC address from the list of manufacturers that Tmac includes, it makes for a perfect MAC spoofing if you match it with your network card manufacturer brand.

Change computer MAC address manually 

Change a MAC address in Windows: Go to Start>Network Connections>Network Sharing Center (Vista) (Network and Dial-up on XP)>, choose Adapter Settings, right click and choose Properties>Configure, Network Connection Properties>Advanced tab, review the list for “Physical Address” or “Ethernet Address” (each NIC utilizes a different name), click on Properties once you have found it, click next to Value and  input your desired MAC address, the computer will have to be rebooted for the changes to take effect.

Change a MAC address editing the registry: You could change a network card MAC address editing the Windows registry, the address will be found around HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\ one of the subkeys labeled NetworkAddress contains it, you could cause serious damage to your operating system and need to reinstall it if you make a mistake editing the registry.

Change MAC address in Linux: Become root and use the ifconfighw command or GNU MAC changer.

Change MAC address in FreeBSD: Become root and use the ifconfig command with three steps.

  • ifconfig {name of the interface} down
  • ifconfig {name of the interface} hw ether {new MAC address}
  • ifconfig {name of the interface} up

Tip: Network administrators could be filtering access to the network based on a device MAC address, changing it while being part of a network could lock you out.

Note: MAC address changing software does not  modify the embedded network card address physically, it instructs Windows (example OS) to use the MAC address specified in the registry.

Change a router MAC address

A router MAC address can be emulated/changed through the router interface, the process is known as MAC cloning, not all routers have this ability, the cheap ‘free’ router given to you by your ISP is unlikely to allow this.

Each device has its own interface and it is not possible to write instructions for all routers, read the router own instructions or make sure that you have a high end router and search the interface advanced configuration options for “MAC cloning”,  in advanced configuration mode you should be able to enter a new MAC address, after which you will be asked to reboot./em/em

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