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[return to "Malware can turn off webcam LED and record video, demonstrated on ThinkPad X230"]
1. sbarre+T1[view] [source] 2024-11-27 20:27:36
>>xairy+(OP)
I thought the whole point of these camera LEDs was to have them wired to/through the power to the camera, so they are always on when the camera is getting power, no matter what.

Having the LED control exposed through the firmware completely defeats this.

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2. perchi+e5[view] [source] 2024-11-27 20:47:53
>>sbarre+T1
For what it's worth, you could just power on the camera, take a pic, then turn it back off instead. Provided you can do this fast enough, an indicator LED is rendered worthless. So you'd need to make the indicator LED staggered, to stay lit for a minimum amount of time.

There's also the scenario where the LED or the connections to it simply fail. If the circuit doesn't account for that, then boom, now your camera can function without the light being on.

Can't think of any other pitfalls, but I'm sure they exist. Personally, I'll just continue using the privacy shutter, as annoying as that is. Too bad it doesn't do anything about the mic input.

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3. akira2+so[view] [source] 2024-11-27 23:20:19
>>perchi+e5
LEDs are diodes. So you can run power _through_ them. Power Supply -> LED -> Camera.
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4. xxs+cH[view] [source] 2024-11-28 02:47:17
>>akira2+so
While true, the amount of power would be too low, LEDs also have quite high forward voltage (~3V for blue ones) and they are current driven devices. That suggestion would require pass all the current through the LEDs. LEDs don't like to be reverse biased either. Overall, it's a rather appalling idea. On top of the fact that LEDs can fail short.

More also you'd want a hold up time for the light (few seconds at least), as taking pictures would flash them for 1/60 of a second or so.

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5. akira2+dN[view] [source] 2024-11-28 04:03:23
>>xxs+cH
They have high forward voltage /drop/ which is a useful property. You drive them with constant current for constant brightness and improved lifespan which is most pertinent for LED light bulb replacements than it is for a simple signal status light. Fixed delay before standby isn't hard to enforce either.

Even so this whole attack vector isn't solved with this. How long should the light stay on for after the camera is put in standby before a user considers it a nuisance? 5 seconds? So if I turn my back for longer than that I'm out of luck anyways.

The anti-TSO means would be a hardware serial counter with a display on the camera. Each time the camera is activated the number is incremented effectively forming a camera odometer. Then if my previous value does not match the current value I know it's been activated outside of my control.

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6. xxs+671[view] [source] 2024-11-28 08:23:30
>>akira2+dN
I meant the forward voltage (also not a constant one) in series with the actual load.
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