When the only USB-A magnetic breakaway coupler on the market became out of stock and EOL'd, we raised $18,507 on CrowdSupply in early 2022 to manufacture our own injection-molded cable. One thousand logistics challenges later, Mouser started shipping BusKill cables to our backers in October 2022.
Now that the hardware is out the door, we're hard at work on new features for the BusKill app. Our top goal is to add a soft-shutdown trigger to the existing lock-screen trigger. At the time of writing, this is functional on Linux and Windows. We're just working out the kinks of privilege escalation on MacOS.
This post will describe how to use BusKill as a dead man switch to trigger your laptop to self-destruct if it's physically separated from you. This guide is specific to QubesOS users.
What if someone literally steals your laptop while you're working with classified information inside a Whonix DispVM? They'd also be able to recover data from previous DispVMs--as Disposable VM's rootfs virtual files are not securely shredded after your DispVM is destroyed.
I'm sure your QubesOS laptop has Full Disk Encryption and you're using a strong passphrase. But what if someone literally steals your laptop while you're working with classified information inside a Whonix DispVM? Not only will they get access to all of your AppVM's private data and the currently-running Whonix DispVM's data, but there's a high chance they'd be able to recover data from previous DispVMs--as Disposable VM's rootfs virtual files (volatile.img) are not securely shredded after your DispVM is destroyed by Qubes!
Let's say you're a journalist, activist, whistleblower, or a human rights worker in an oppressive regime. Or an intelligence operative behind enemy lines doing research or preparing a top-secret document behind a locked door. What do you do to protect your data, sources, or assets when the secret police suddenly batter down your door? How quickly can you actually act to shutdown your laptop and shred your RAM and/or FDE encryption keys?
BusKill utilizes a magnetic trip-wire that tethers your body to your laptop. If you suddenly jump to your feet or fall off your chair (in response to the battering ram crashing through your door) or your laptop is ripped off your table by a group of armed thugs, the data bus' magnetic connection will be severed. This event causes a configurable trigger to execute.
This post will describe how to add a trigger that initiates a "self-destruct" sequence when your BusKill laptop kill cord's connection is severed--rendering your data permanently & irrevocably destroyed in the event that your laptop were physically separated from you (ie: by a snach-and-run thief).
Many people were disappointed when the original post introducing BusKill only alluded to a self-destruct trigger, without actually describing how to use it with BusKill. This was done for two reasons:
Most people probably don't actually want an accidental false-positive to destroy all their data and
A self-destruct sequence should be taken seriously. Its implementation should be thoroughly thought-out, tested, and forensically analyzed
This article will provide that thorough analysis and explain to the reader how to implement a self-destruct trigger with BusKill on linux machines that have FDE with LUKS.