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Are USB-cables safe?

asked 2018-08-05 12:28:15 +0200

Jollallinen gravatar image

Am I just paranoic? Xperia X is asking for pin-code after plugging in to a charger with one certain USB-cable. After entering the code the next question is if I want to charge the phone, use media transfer or enter developer mode. Not all cables require password for charging the phone. This cable "works" the same way with all chargers. Is it safe or can the cable be hacked somehow? The cable and charger it belongs to came with a cheap Bluetooth headset.

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Most people have a smartphone these days, can you borrow a cable from a neighbour or friend to test with?, it does sound a bit odd, but I wouldn't put it past Sony to have some kind of proprietary measure for recognising cheap/nasty/dodgy cables/chargers in order to protect the device at some level.

Edz ( 2018-08-05 14:19:44 +0200 )edit

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answered 2018-08-05 20:42:14 +0200

Mohjive gravatar image

updated 2018-08-05 21:26:00 +0200

A charger normally has D+ and D- connected to signal to the device that it has charging capability only. But if those pins are not connected in the charger or that the cable is broken for any of those connections the device will think the charger has data capability and then you will get that question from your Sailfish device.

Generally chargers (and cables) bought in a store are safe. There's no way to collect data through the power grid and instead it has to be done wirelessly. And the overhead cost of creating and distributing such charger is too big without knowing if it pays off or not.

Instead it's much more effective to create an attack at a public USB charging station (normal power outlets where you bring your own charger are still safe) such as an airport or café. In those cases I would use a USB "condom". You can either buy one or create one yourself.

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^ this. And the fact that you're asked for unlock code is a security feature itself. Your phone will not allow any connection with the over data pins unless you unlock it and select either Media Transfer or Developer Mode, so you should be fine. The fact that your cable is misbehaving in this way is kinda weird though. Maybe it's just damaged as @Aldrog suggested?

pisarz1958 ( 2018-08-06 00:32:40 +0200 )edit

answered 2018-08-05 13:22:02 +0200

updated 2018-08-05 13:23:18 +0200

In theory the charger might actually be a more complex device that tries to hack connected devices. But I'm not that paranoic so I'd assume it's just a damaged cable 😉.
For example I have a USB cable I didn't treat very carefully so recently it either charges the phone normally or causes the phone to ask for connection type (as you described) or doesn't charge at all.

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answered 2018-08-05 18:28:22 +0200

Jollallinen gravatar image

I am using USB chargers where I can change the cables from one device to another. This cable and the charger are quite new, a couple of months old and it hasn't been used a lot. I can use the charger with another cable without problems and I can use other chargers with their own cables. Only this single cable, not the charger, is causing problems. If I unlock my Xperia X / Sailfish latest version device the cable will charge. I haven't tried the other modes just to be on the safer side.

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I have similar situation: some cables start charging immediately and some ask the question. Biggest difference seems to be that when I respond to the question it does not start charging. Instead it gives cable removed notification and asks again.

potski ( 2018-08-05 23:09:33 +0200 )edit
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Asked: 2018-08-05 12:28:15 +0200

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Last updated: Aug 05 '18