MAC address spoofing

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There are two methods for spoofing a Media Access Control (MAC) address on Arch. Both of them are outlined below.

Method 1: macchanger

The first method uses macchanger (a.k.a., the GNU MAC Changer). It provides a variety of features such as changing the address to match a certain vendor or completely randomizing it.

Install the package macchanger from the Official Repositories.

After this, the MAC can be spoofed with a random address. The syntax is macchanger -r <device>.

Here is an example command for spoofing the MAC address of a device named eth0.

# macchanger -r eth0

To randomize all of the address except for the vendor bytes (that is, so that if the MAC address was checked it would still register as being from the same vendor), you would run the command:

# macchanger -e eth0

Finally, to change the MAC address to a specific value, you would run:

# macchanger --mac=XX:XX:XX:XX:XX:XX

Where XX:XX:XX:XX:XX:XX is the MAC you wish to change to.

Note: A device cannot be in use (connected in any way or with its interface up) while the MAC address is being changed.

Method 2: Manual

First, you can check your current MAC address with the command:

# ip link show eth0

The section that interests us at the moment is the one that has "link/ether" followed by a 6-byte number. It will probably look something like this:

link/ether 00:1d:98:5a:d1:3a

The first step to spoofing the MAC address is to bring the network interface down. You must be logged in as root to do this. It can be accomplished with the command:

# ip link set dev eth0 down

Next, we actually spoof our MAC. Any hexadecimal value will do, but some networks may be configured to refuse to assign IP addresses to a client whose MAC does not match up with a vendor. Therefore, unless you control the network(s) you are connecting to, it is a good idea to test this out with a known good MAC rather than randomizing it right away.

To change the MAC, we need to run the command:

# ip link set dev eth0 address XX:XX:XX:XX:XX:XX

Where any 6-byte value will suffice for 'XX:XX:XX:XX:XX:XX'.

The final step is to bring the network interface back up. This can be accomplished by running the command:

# ip link set dev eth0 up

If you want to verify that your MAC has been spoofed, simply run ip link show eth0 again and check the value for 'link/ether'. If it worked, 'link/ether' should be whatever address you decided to change it to.

Spoofing the MAC address

With netcfg

Put the following line in your netcfg profile to have it spoof your MAC address when it's started:

PRE_UP='macchanger -e wlan0'

You may have to replace wlan0 with your interface name.

Systemd Unit

Same thing with systemd:

/etc/systemd/system/macspoof@.service
[Unit]
Description=MAC address change %I
Before=dhcpcd@%i.service

[Service]
Type=oneshot
ExecStart=/usr/sbin/ip link set dev %i address 36:aa:88:c8:75:3a
ExecStart=/usr/sbin/ip link set dev %i up

[Install]
WantedBy=network.target

You may have to edit this file if you do not use dhcpcd. Note: This works without netcfg. If you are using netcfg, see above.

See also