Gear to Block ‘Juice Jacking’ on Your Mobile

Ever since I learned about the threat of “juice-jacking” — the possibility that plugging your mobile device into a random power charging station using a USB cord could jeopardize the data on that device — I’ve been more mindful about bringing a proper power-outlet charging adapter on my travels. But in the few cases when I forgot or misplaced the adapter, I’ve found myself falling back on one of two devices I’ll review today that are both designed to block USB charging cords from transmitting data.

The USB Condom, in action at 35k feet.

The USB Condom, in action at 35k feet.

Juice-jacking as a threat probably first crept into the collective paranoia of gadget geeks in the summer of 2011, after I wrote a story about two researchers at the DefCon hacker convention in Vegas who’d set up a mobile charging station designed to educate the unwary to the fact that many mobile devices (particularly Apple devices) are set up to connect to a computer and immediately sync data.

Their proof-of-concept was a reminder that in the (admittedly unlikely) event that a clever attacker managed to hide a small computer inside of a USB charging kiosk, he might be able to slurp up your device’s data.

Since that story, several products have sprung up to help minimize such threats. These small USB pass-through devices are designed to allow charging yet block any data transfer capability. The two products I’ve been using over the past few months include the “USB Condom” and a device called the “Juice-Jack Defender.”

Both prophylactics (cue the crude jokes) function the same way — with male and female USB adapters at either end — but the two have a slightly different form factor and feel. True to its name, the USB Condom is a rectangular black circuit board wrapped in a clear plastic sheath, measuring approximately 54 millimeters/2 inches long and 20 mm/.75 inches wide.

The Juice-Jack Defender is slightly smaller — about 45 mm long and roughly 16 mm wide — and is wrapped in rubberized black plastic, although the device picture on the Web site of the vendor,, shows a product coated in blue plastic.


Both perform their meager jobs admirably (without pause or interruption), and so from a functional perspective are indistinguishable. Overall, the Juice-Jack Defender feels much sturdier — as if it would hold up just fine to an inadvertent nudge in an upward or downward direction while charging. I’m not sure I could say the same about the USB Condom, although to be honest I didn’t stress-test either device.

Beyond size and durability, the only difference between the two products may be the price; Charge Defender is only taking pre-orders, and the company hasn’t yet listed a price for the Juice-Jack Defender. The USB Condom retails for $9.99 (with free shipping).

As I noted in my 2011 story, the safest route for charging your device on-the-go is to use the supplied power cord that plugs into a regular electrical outlet (assuming you can find an available outlet). Battery-powered mobile charging devices also work well in a pinch and are available at many airports. If you must use a random charging kiosk, the safest option may be to completely power off the device before plugging it in.

I’ve found myself digging through my backpack for these devices when I’m out and about and bereft of an outlet and the only option is juicing up at a public kiosk (or someone else’s computer!). If nothing else, these little buggers are a great conversation starter; the woman seated beside me on the plane where the above picture was taken had never heard of juice-jacking and was instantly fascinated. Turns out, she ran a small business and had no clue about the risks she faces when banking online with her business checking account (she does now!).

The USB Condom (top) and Juice-Jack Defender, side by side.

The USB Condom (top) and Juice-Jack Defender, side by side.

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