Image: USBKill.com

For just a few bucks, you can pick up a USB stick that destroys almost anything that it's plugged into. Laptops, PCs, televisions, photo booths -- you name it.

Once a proof-of-concept, the pocket-sized USB stick now fits in any security tester's repertoire of tools and hacks, says the Hong Kong-based company that developed it. It works like this: when the USB Kill stick is plugged in, it rapidly charges its capacitors from the USB power supply, and then discharges -- all in the matter of seconds.

On unprotected equipment, the device's makers say it will "instantly and permanently disable unprotected hardware".

You might be forgiven for thinking, "Well, why exactly?"

The lesson here is simple enough. If a device has an exposed USB port -- such as a copy machine or even an airline entertainment system -- it can be used and abused, not just by a hacker or malicious actor, but also electrical attacks.

"Any public facing USB port should be considered an attack vector," says the company. "In data security, these ports are often locked down to prevent exfiltration of data, or infiltration of malware, but are very often unprotected against electrical attack."

Not every device is vulnerable to a USB Kill attack. The device maker said that Apple "voluntarily" protected its hardware.

USB Kill costs €49.95 (about $56), and a Test Shield, which allows users to test for an attack without blowing up their hardware, costs an additional €13.95 (about $16).