From: Razer <Rayzer@riseup.net>
   On 10/15/2015 03:22 AM, Georgi Guninski wrote:
   >> [1]http://www.theregister.co.uk/2015/10/14/sneaky_220v_usb_fries_lap
   tops/
   >> An internet mischief maker has built a USB stick that delivers
   dangerous
   >> 220-volt shocks to PCs, destroying them in the process.
   >Tentatively speaking, No. I don't think so... The circuitry is
   designed
   >for 5 volts, and the capacitance available throughout the device is so
   >low almost no current would be available either.
   Sorry, but you are wrong there.  The amount of power available through
   a typical USB connection is probably many hundreds of milliamps, at 5
   volts.  And this power could be converted, by a switching power supply,
   to hundreds or even thousands of volts, and stored in an internal
   capacitor.  Once switched on, internally, and applied back to the data
   signals, the device could easily fry a few levels of circuitry in the
   computer.  It would be essentially unrepairable.
              Jim Bell, N7IJS.   The World's Last Tech-Plus Ham

References

   1. http://www.theregister.co.uk/2015/10/14/sneaky_220v_usb_fries_laptops/