The myth that to delete data really securely from a hard disk you have to overwrite it many times, using different patterns, has persisted for decades, despite the fact that even firms specialising in data recovery, openly admit that if a hard disk is overwritten with zeros just once, all of its data is irretrievably lost.
Craig Wright, a forensics expert, claims to have put this legend finally to rest. He and his colleagues ran a scientific study to take a close look at hard disks of various makes and different ages, overwriting their data under controlled conditions and then examining the magnetic surfaces with a magnetic-force microscope...
They concluded that, after a single overwrite of the data on a drive... the likelihood of still being able to reconstruct anything is practically zero...
Nevertheless, that doesn't stop the vendors of data-wiping programs offering software that overwrites data up to 35 times, based on decades-old security standards that were developed for diskettes...
Something much more important, from a security point of view, is actually to overwrite all copies of the data that are to be deleted. If a sensitive document has been edited on a PC, overwriting the file is far from sufficient because, during editing, the data have been saved countless times to temporary files, back-ups, shadow copies, swap files ... and who knows where else?
All text credit to the H-online. Very interesting.
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