Does the magnet affect USB webkeys or USB drives ?

Definitely no. USB webkey and USB drives are much difference from floppy disk or hard drive. Floppy disks and hard drives work through magnetic cells and it will be affected by outside magnet. USB webkey and USB drives don't have such magetic resources which can be affected by outside magnet so it can work well even after long touch of outside magnet.

These concerns and are really unfounded for a simple reason. Flash drive memory is solid state and so has no moving parts and the data is stored as electrons and not changes in magnetic flux (as with floppy disks and hard drives). There is a direct quotation from Bill Frank, executive director of the CompactFlash Association (CF cards use the same types of memory chips as USB sticks to store data) that gives humorous (if slightly scary!) comfort to the security of your USB data. He says:

"A magnet powerful enough to disturb the electrons in flash would be powerful enough to suck the iron out of your blood cells"

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