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Comment by fernly | Hacker News Reader

Somewhat more specific info on Wikipedia[1]. Easy prevention is a "USB Condom", a USB cable with the data lines blocked[2][3].

Edit: those devices seem to be only for USB 2 type A connections. Anyone know of other format "condoms" eg mini-A or type 3?

[1] https://en.wikipedia.org/wiki/Juice_jacking

[2] https://www.usbcondom.org/

[3] http://syncstop.com/

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PortaPow offers a variety of cables including A to micro-B, A to lightning, and A to C[1].

Adafruit's website sells a lot of cables[2], including

* An A extender blocking data with a switch to turn power on and off

* An A to micro-B blocking data with a switch to turn power on and off

* An A that splits to mini-B blocking data and micro-B allowing data

* A micro-B extender splitter where one side has only power and the other side has power and data

* An A extender that always allows power and has a switch to turn data on and off

* An A to micro-B that always allows power and has a switch to turn data on and off

* An A to triple splitter of lightning with data and power, 30pin iPhone/iPod with only power, and micro-B with only power

There are other similar cables[3]. Note that naively disabling data will sometimes disable fast charging. Some data-blocking cables themselves re-implement or allow fast charging.

I thought essentially no one uses mini-A or micro-A, so I don't know why you would want that. I thought USB 3 was just about faster data. If a cable always blocks data, then I don't see any use for USB 3.

[1] https://portablepowersupplies.co.uk/home/micro-usb-data-bloc...

[2] https://www.adafruit.com/category/142

[3] https://www.newegg.com/multi-color-monoprice-4-50-ft-usb-cab...

> I thought essentially no one uses mini-A or micro-A, so I don't know why you would want that. I thought USB 3 was just about faster data. If a cable always blocks data, then I don't see any use for USB 3.

Presumably, if fernly wants a mini-A, it's because they do use it and that's why they want it. USB 3, I would assume USB-C was meant, and that becomes an issue of plug shape.

I'm interested in what devices fernly has that use mini-A.

IIRC the data lines are required for the phone to charge quickly. Without them you're limited to just 500 mA instead of up to 3 A.

Shorting the data lines together lets the phone know it can draw up to 2A.

My solution is a usb- chargable backup battery.

Might want to check whether the battery includes a hub. I was surprised to find that my Dell power bank does, which is great because I can get photos off my phone while I charge both the phone and my laptop, but would negate any protection in this scenario.

Thanks for the heads-up! Happily, my battery doesn't have that feature.

Is it possible for the usb powerbank to carry a virus? It might not be as safe as you hope. Of course it shouldn't accept any data, but considering how poorly ports and devices are often secured, I bet that quite a lot of them do accept data.

But why do USB devices even accept unauthorised data at all? There's probably a good reason for it that I don't understand, but it seems to me it's rather obvious that blindly accepting data from unknown devices is quite a big security risk. And yet I keep seeing these new data port standards (USB, thunderbolt, etc) that just blindly trust whatever gets connected to it, and allow it unreasonable control over the device. I guess the reason is that you want to be able to plug a new keyboard into your PC and have it just work.

Because having physical access to a device is not "unauthorized". It's like asking why does the body automatically get every virus and bacteria from every surface that you lick, "it should be more thoroughly checked"...

Or maybe the user just shouldn't give physical access to devices that are not trusted.

Your argument, in case of computing devices (which means with well-defined physical connectors, as opposed to wetware), boils down to "just because." Android and iOS used to ask for permission, a long time ago - but it was dropped as "not user friendly". So, the problem is not "impossible to do", merely "inconvenient w/r/t other goals".

As for not giving physical access...easier said than done. Looking around, I see multiple such devices lying around here, with the owner within 20 m, but not paying attention. IMNSHO asking for authorization is far more logical than assuming "whoever can get their hands on it is authorized."

But physical access is everywhere, as these charging points show. And a USB drive is really easy to hide and stick into anything. Automatically trusting something that's super common and easily compromised is a really bad idea.

That's good. Plug in the battery at the station, "here, jack this." Plug your phone into the output jack of the battery.

The charge controller doesn't allow simultaneous charge and discharge. It might allow simultaneous charge and power. The concern is, if your power pack does let you power devices while charging the battery, it's passing the power straight through from the wall, not via the battery. Is it also passing the data lines straight through? Not sure, you'd have to check the schematics. Here's an example... a great board, I own one, but I have no idea if the data lines are isolated: https://www.adafruit.com/product/2465

They usually say not to charge the battery and draw from it at the same time. They never say why.

So, get two batteries, and charge one while using the other to charge. Plus, you then have a charged backup battery...

Follow the money: a system which only works in one mode or the other at a time is an order of magnitude easier to design/debug/manufacture than a system that needs to work in one mode, other mode, both at the same time, and seamlessly switch between these (=> also cheaper).

To dissuade you from charging the battery from the battery itself.

Passthrough creates a lot more heat, and that heat hangs around longer, which is not good for the battery. I think Anker said that.

You can stack on a cable-less adapter or perform surgery on one to make its data lines unusable.

That will limit the amount of power you can draw to 500ma. The data lines are needed to negotiate power supply above that e.g. quickcharge standard.

A proper usb condom has some smarts which acts as a middleman, that only passes traffic relating to power negotiation.

The "manual" for my portapow cable claimed to not even pass on that, but instead negotiate with the upstream and downstream, speaking several protocols.

Back in the days of the iPad 3, there were active adapters that intermediated, lying to both charger and device and permitting the iPad to charge at full current rather than 500mA, and completely blocking access to the data lines as a side effect. I still have a couple, and use them to great effect to charge my Android device more quickly on the thin clients at work as well as protect myself from juicejacking.

Love these names.

Juice jacking, USB condoms and what not. Sometimes I feel we need more funny sounding names across the tech industry.

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