BusKill, a $20 USB Dead Man’s Switch for Linux Laptop

Pierluigi Paganini January 04, 2020

BusKill‘ is a cheap kill cord Dead Man Switch to trigger the machine to self-destruct in case the laptop is stolen, it was designed by the software engineer Michael Altfield.

The idea is very simple, the BusKill cable connects a Linux laptop to the user, for example, to his belt. In case of theft, the USB cable disconnects from the laptop and triggers a udev script that executes a sequence of operations, from shutting down to completely wipe the device or delete certain sensitive data on the disk.

“Surprisingly, I couldn’t find a low-tech solution that implements a laptop kill cord, so I decided to build one myself for ~$20 and a simple udev rule.” wrote the expert in a blog post.

“We do what we can to increase our OpSec when using our laptop in public-such as using a good VPN provider, 2FA, and password database auto-fill to prevent network or shoulder-based eavesdropping,” says Altfield. “But even then, there’s always a risk that someone could just steal your laptop after you’ve authenticated!”

The expert published a video showing BusKill triggering a kill signal when the magnetic breakaway is tripped.

Altfield published the instructions to build the BusKill cables just buying a few components for a price ranging from $20 up to $45:

  1. A cheap $4 USB drive with durable keyring hole
  2. A small & strong carabiner keyring for attaching the above drive to your belt loop (I like this $6 one because it’s small, well-made, and has a clever locking mechanism)
  3. $7 USB magnetic breakaway adapter to plug into the computer’s USB-A port
  4. And finally, a $3 1-meter USB extension cable to connect them

The expert published two sample udev scripts that lock the device by activating the screensaver and shuts down the laptop respectively.

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Pierluigi Paganini

(SecurityAffairs – BusKill, hacking)

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