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For example, how could I measure the normal power consumption of my USB keyboard?

After I get my statistics, I may easily notice when a hardware keylogger gets installed, by the changed power consumption.

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What is your real question or problem? Do you want to know how much your keyboard consumes (if so, why)? Do you actually just want to know whether there's a keylogger installed? Is your question purely hypothetical or are you in a situation where you suspect a keylogger being installed? – slhck Jun 8 '12 at 16:13
If a hardware keylogger is installed, you should notice by actually seeing the device sitting between the usb port and the keyboard connector. – psusi Jun 8 '12 at 23:46
The question is hypothetical. I'm just curious about how to know the consumption for no particular reason. On the other hand, a hardware keylogger would be installed inside the case of my keyboard, I think. Then it would be hard to spot, or else it would be pointless. – n611x007 Jun 9 '12 at 7:07
This question is off topic per the Site Help "You should only ask practical, answerable questions based on actual problems that you face." – Scott Chamberlain Jun 10 '13 at 14:31
@ScottChamberlain interesting point. I think I face the problem that I cannot test another problem without a tool to measure it. How could I face the problem of having a logger installed into my keyboard if I cannot check if I face it? :) So the way to check it is a problem itself. – n611x007 Jun 10 '13 at 14:39
up vote 10 down vote accepted

USB current/voltage meters exist. Here's one on Amazon (though unfortunately out of stock at the moment). Here's the same model on eBay (from Germany, but ships worldwide).

enter image description here

Alternatively, if you're up for a bit of DIY, see this project on Instructables. You'll need a multimeter, though, because that's just a passive passthrough connector that simply provides a couple of test points.

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Thanks, I like it. I'll wait a bit to see if a computer-based solution comes up, in case if it's possible. On the other hand the computer would be also a target for such an attack, while a newly bought/made usb c/v meter won't. :) – n611x007 Jun 9 '12 at 7:11
i'll just provide some further identification related things from your links PC Computer Check Diagnostic USB Port Voltage Current Tester Checker Extend Cable by Winter El. Co. on amazon. And, UPT- 0049 USB-Port-Spannungs- + Strommesser [7739] on ebay from seller m-ware. I could ask him re this... but could ask you perhaps. I see it's rectangular. On one side is a USB cable hardwired in, on the other There is a female usb socket and a power supply socket on it. does it need the power supply socket, and for what? – barlop May 9 '13 at 9:45
+1 just to add. I have tried the device, and while it has the socket, no power supply is necessary(so who knows why it's there). it has a little switch for volts or amps, and shows volts and amps nicely. though it hasn't given me any insight into why my usb hdd is recognized in one computer and not another. The one I got , same thing, on ebay, was called PC USB 2.0 Cable Device Voltage Current Meter Tester Item Number 290754313719 $14.25 USD – barlop May 9 '13 at 11:52
The above device is hard to find now though there is USB charger doctor… and – barlop Oct 17 '13 at 3:46

You didn't specify, but I know Windows (and probably other modern OS's) will tell you how much power is "required" for each attached USB device in the properties of each "USB Root Hub" in the Device Manager.

USB Root Hub Properties

Regardless of that, unless you're talking about a physical hardware keylogger that has to be in-line with the keyboard, then you're not going to be able to detect it by electrical draw in the way you are suggesting (by watching the keyboard).

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Please note that the "Power required" data is whatever the usb devices is reporting as its maximum, it's not an actual measurement. Nothing prevents a device from reporting 100 mA and actually drawing more (up to a limit, of course). So, if you have an in-line keylogger, it will not be reflected here since the USB keyboard does not know about it. – haimg Jun 8 '12 at 17:43
@haimg and techie007, Thanks for both answer and comment. – n611x007 Jun 9 '12 at 6:59

I would recommend this USB power meter...

I use it and it works great. Better than hacking up cables and trying to tie in a multimeter.

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worth knowing, but worth noting that the one you suggest is many times more expensive than one or two already mentioned. though your has some longevity in availability,as it's still sold. – barlop Oct 17 '13 at 3:49

Just to add Mac info to the overall solution…

You can see data for each hub & device from
 menu > About this Mac > System Report > USB...

enter image description here

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This still has the added problem it will still report what the device says is the case. – Ramhound Feb 4 '15 at 19:20
Not sure it does, but don't have any hard proof - I have devices that show 'available 500, required 8' etc. As the OP was worried about a key logger - if one was there, it would at least show in the list, whatever its power requirement was [edit - more I re-read the OP, more paranoid it sounds - I doubt there's any real answer to that] – Tetsujin Feb 4 '15 at 19:24
I am pretty sure it does. A USB device can report itself has anything it wants during that initial communication to determine what drivers will be needed to communicate with it further. – Ramhound Feb 4 '15 at 19:28

I haven't tried it but you could get a regular Mains Power Meter plug and unplug the keyboard and measure the difference.

What I have tried, is you could also connect a multimeter in series and measure the current. Like break the usb cable and connect your multimeter in between. If somebody can describe that process fully then that'd be great and a better answer than mine. Given the Voltage(5V) and current/amps, you can measure the Power/watts.
Power(P) = Current(I) * Voltage(V)

added- now tried indrek's solution.. PC USB 2.0 Cable Device Voltage Current Meter Tester

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There seems to be one at AdaFruit, called USB Charger Doctor. It looks simple, but efficient.

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I see they ship from New York. "International orders are shipped using USPS which is the US Postal Service." In recent lights, this may (unfortunately) also be relevant: NSA reportedly installing spyware on US-made hardware – n611x007 Aug 8 '14 at 14:35

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