The smartphone's ever growing ubiquity has led to the rise of public kiosks for recharging smartphones. These have been appearing in airports, malls and food courts, and come in both free and paid-for variants. The question is, are they safe to use? After all, putting a strange jack in your socket isn't always the best idea.

The proliferation of these kiosks has led to a new type of hack called "juice jacking".

The gadget is described by Crowd Supply, who sells the product, as ‘a protective barrier between your device and "juice-jacking" hackers.’

One of the biggest risks for iPhones, according to the documents, is being plugged into an unsecured outlet for recharging. Security experts such as Brian Krebs have warned of the (possibly hypothetical) risk of "juice jacking" — rogue charging kiosks at airports or conventions secretly copying data from a victim's phone.

You don’t have the power cable needed to charge the device, but you do have a USB cord that can supply the needed juice. Then you spot an oasis: A free charging kiosk. Do you hesitate before connecting your phone to this unknown device that could be configured to read most of the data on your phone, and perhaps even upload malware?