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If you have security auditing skills you are more than welcome to review our [[design|contribute/design/MAC_address]] and [[implementation|contribute/design/MAC_address#implementation]].
Every network device (wired, Wi-Fi/wireless, 3G/mobile) has a [[!wikipedia 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](http://nightly.tails.boum.org/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
What to test
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
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 whitelisting problems
Some wireless networks are configured to only allow connections for devices with certain MAC addresses, called MAC address whitelisting. 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 whitelisting, then connect to it with MAC spoofing enabled and verify that Tails shows a notification with the headline: "Network connection blocked?".