You can help Tails! The MAC address spoofing feature is ready for testing. This feature prevents geographical tracking of your network devices (and by extension, you) by randomising their MAC addresses.

If you have security auditing skills you are more than welcome to review our design and implementation.

Background

Every network device (wired, Wi-Fi/wireless, 3G/mobile) has a MAC address, which is a unique identifier used to address them on the local network. Broadcasting a unique identifier in this manner introduce a couple of potential privacy issues for Tails users. Geographical location tracking is the main one: observing a MAC address at a particular location and time ties the corresponding device to the same location and time. If the real identity of the device's owner is known, their movements can be determined. To prevent this one can temporarily change the MAC address to something random at each boot, which is referred to as "MAC address spoofing".

How to download the test image

Download the latest test ISO from build_Tails_ISO_devel. Keep in mind that this is a test image. Do not use it for anything else than testing this feature.

How to use MAC spoofing in Tails

MAC spoofing is enabled by default in this test ISO. You can change this with a startup option. The (preliminary) MAC spoofing documentation tries to explain situations where it actually may be a bad idea to keep this option enabled. However, as this is just a test version we of course urge you to not use it for anything serious, and if possible, to test both to enable and disable the option.

What to test

For any MAC spoofing-related issues you experience using this test ISO, please include the output from the following commands when reporting it to us (note: it requires setting an administration password):

sudo grep spoof-mac /var/log/syslog
sudo grep unblock-network /var/log/syslog

In particular, we would like you to pay extra attention to the following things:

Verify that the MAC spoofing setting is enforced

Please verify that the MAC spoofing setting you select actually is enforced by issuing the following commands:

. /usr/local/lib/tails-shell-library/hardware.sh
for i in $(get_all_ethernet_nics); do
  echo "Interface $i"
  macchanger $i
done

For each network device you'll get an entry looking something like this:

Interface eth0
Permanent MAC: 12:34:56:78:90:ab (unknown)
Current   MAC: 12:34:56:f4:fb:22 (unknown)

The "Permanent MAC" is the network device's "real", unique MAC address; the "Current MAC" is whatever it is set to at the moment, spoofed or not. In other words:

• if they are different, then MAC spoofing is enabled;

• if they are the same, then MAC spoofing is disabled.

Please report if you ever get unexpected results.

MAC address allowlisting problems

Some wireless networks are configured to only allow connections for devices with certain MAC addresses, called MAC address allowlisting. MAC address spoofing will cause issues on networks like these. Therefore Tails has a crude mechanism for detecting this, and will show an informative notification about what to do about it.

If you have access to a wireless network that employs MAC address allowlisting, then connect to it with MAC spoofing enabled and verify that Tails shows a notification with the headline: "Network connection blocked?".

Note: Tails detection mechanism for MAC address allowlisting only works for wireless (Wi-Fi) networks.

Network problems

Please report all network device and connection issues, e.g. if any of your network devices do not get detected by Tails at all, if the network connection fails, or if the network connection succeeds but actually does not work. Also check whether you experience the same issues using Tails 0.22.

Known issues

No fail-safe for hotplugged devices after logging in

In order to prevent the real MAC address from leaking when MAC spoofing fails for some network device, Tails has a fail-safe that simply disables the device. At the moment this only works for network devices present before logging in with Tails Greeter; the fail-safe does not work for e.g. Wi-Fi USB dongles hotplugged after that.