How to wipe a USB hard drive

Boot up an Ubuntu live CD, open up the partition editor, and use the dropdown box in the upper right to find the drive with the correct size and contents to be your UBS disk (make sure you get this right, or you could end up wiping the wrong drive!). Make a note of the drive name (it should be something like "/dev/sdX", where X is any letter), open up a terminal, and run:

dd if=/dev/urandom of=[drive]

and then

dd if=/dev/zero of=[drive]

Where [drive] is the name you made a note of.

This will write random bits to the drive and then fill it with zeros. When you are done, you can use the partition editor again to verify that the disk has been wiped.

If you're running Windows 2000 or better there is a built-in command line utility that overwites deleted data making it unrecoverable.

cipher /w:driveletter:\foldername

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