My device thinks a china bought USB wall charger is a computer. Juice Jacking? Virus?

Hi, hoping you could shed some light on this puzzle.

I recently bought This wall charger/travel adaptor and plugged in my Kobo Glo e-reader which prompts me to accept or deny "connection to the computer", just like it does when I plug it into my actual computer. It does not do this with any of my other wall chargers, so I was wondering if there is any reasonable explanation as to why this charger is different?

To be clear I've tried blocking the two middle pins on one of the USB ports, which are the ones carrying data, to make it a "dumb" charger, but my kobo still prompts me. Very strange.

It is possible to weaponise a charger with a embedded processor.. but I do have my doubts. More likely it has a circuit in it so that the phones charge with more amps that acts as if it was a PC host adapter.

Honestly for only charging I advice power only cables as, e.g. on airports, you never know how provides the USB outlet to you and why ;)

Hehe, I know not to plug it into a wall mounted USB in an airport, but thanks for the added advice ;) . However, blocking the two data pins should make it the same as a power only cable, they just short out the middle pins, that way the device thinks it can draw more than 500mA, right? It's still stange that when I've totally blocked those pins, it still prompts me.

Yes, it does not mater how you break the circuit.

Yes, that’s how "dumb" chargers without any logic to negotiate the powerdraw signal that they are in fact dumb.

This could actually be the reason why your device thinks its a PC as D+ and D- are not shorted.

I see. I have tried prying it open, but have not succeeded... yet. but do you reckon I can just go ahead and short them out? If nothing else just to troll it if it actually does try to introduce something I'm not interested in.

When I get it open, will I be able to recognize a micro processor in the midst of the curcuit board/transformer? Is there any other way to know if it's trying to harm me?

Sorry, when I need these technical phrases it's my english that shorts out.. by transformer I mean there must be a circuit board for voltage convertion and DC power.

From the size of the device I guess it does not actually utilize a transformer (big coils, metal core) but a high frequency switching converter... a buck converter.

If you really pry it open I would make pictures, post them and than throw it away. There likely is no protective circuitry in a Chinese wonhanglow product.

If you have a multimeter at hand, try and measure the D+ and D- of the charger if they are shorted or not. Just shorting them.. you can try but I would not atatch my expensive devi

Are you saying it is worthless after I pry it open, or is it worthless either way?

Ok, I will try measuring it, but I do not have a working multimeter at hand right now.

Thanks a lot for your responses man, has really helped me :)

In order to open it up I'd recommend a hammer and a flat head screwdriver. Make sure your tools won't transfer electricity as well. Last thing you want is a few volts of electricity pulsating through you....unless you're into that.

The likelihood of it getting damaged when prying open, the likeliness its not abiding the safety regulations it states, the fact you cant seal the housing any more.. and it should be savetyisolated... all that.

ALWAYS disconnect! I do not expect any high capacity mains capacitors to be in there.. so unplugging it and letting it rest for a moment should be enough to get rid of any charge.

I can sort of open it halfway with just my fingernails, so I don't think it is glued together or anything. Haha, no, I'd disconnect and wait for the capacitors (if there are any) to discharge.

Since the prying seems like a bad idea and I don't have a multimeter at hand, I thought I could at least test your thesis that if D+ and D- is not shorted out, it will prompt me because it thinks it's a computer. So I took one of my other wall chargers, checked to see there was no problem when connected normally, I then blocked off D+ and D- with some electrical tape and connected it, and guess what, you were totally right. It prompted me. I then did it all again, just to be sure. So there is that, at least. The mystery is solved. Now I just need to take off my tinfoil hat...

Keep it where it is =)
So as a mater of fact that that charger likely will not be good as devices actually should not draw more than 100mA if more is not negotiated (or D+- shorted)

Haha, I wait a little longer then. If I do get it open without damaging anything I might as well just short them out myself. What a bad piece of engineering though.. Thanks for everything th3z0ne!

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The USB power cable that comes with a Google Chromecast for instance has no data leads in it. You can safely use that for power. It's always better to use only USB cables with data leads if you're really sure you want to transfer data through it. Besides for debugging, there aren't all that many use cases for data through USB any more these days, with all them wireless connections. Chances are that you don't really need a USB data cable any more. Most USB data applications can be solved more efficiently in another fashion, like for instance with a memory card reader or something along those lines.

I'm actually quite curious to see what's inside that wonhanglow charger. Probably similar to the average pyrotechnics ignition circuit. Just kidding, but one never knows.
I'll even give you an out of 10 rating on fire hazard if it warrants it.

Over the years in my various IT jobs in South Africa I've gotten a bit of reputation as the 'magic smoke whisperer' of cheap dodgy equipment. The market down here is just saturated with the stuff, often sold with no safety features, shielding or proper current filtering, particularly with Buck Boost types, their *DC output is often good enough to make a LW radio transmitter. Part of my job description at one point even included hunting down noisy Power devices that where destroying SNR on phone and other network lines.

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My blackberry (blackberries?), Z30 and Passport at least (not tried the older ones for ages), actually ask what you want to do when you connect to a non-trusted device (in my case, that's all minus my corporate laptop right now).

However, what I prefer doing these days is to connect whatever charging option available, to a battery pack, from which in turn I then charge my cell. This means the risk is reduced of a bad USB port taking out my whole phone. Also, a lot of cheap chargers have horrendous quality with a nasty impact on touch screen functionality. My phone is not typically impacted much by that, but say an iPad or a nameless Android tablet I have, they go nuts (in that it thinks you pressed somewhere, whereas you pressed somewhere else entirely).

Another, cheap & cheerful option, is to use charge-only leads. I have a few of those in my backpack and my co-workers appreciate that too, as it means I can guarantee not to be synchronizing their phones to my laptop. It tends to mean charging happens at 500mA rate, but it is a bit safer :)

I have a bunch of normal usb cables, I might just go ahead and make some of them dumb. I do find myself using them for data quite often. Might search for other avenues of transfer now, though.

I don't think I'll pry it open. Too much hassle for maybe
breaking it. I'm a poor student man, don't have the money to throw after
a new one ;)

Interesting CV you got there by the way!

Whoa, you must have some seriously weird power, I've never even heard of it being able to mess with the screen. Makes you wonder what else inside is messed up in the process. I thought there would be capacitors making sure nothing more than what is needed passes through beyond the battery, even before the battery..