Some technical claims, even those emanating from self-avowed IT experts, are better left in the realm of urban legend. Call them "digital legends," if you will.
Over time, I've been repeatedly confronted with a persistent digital legend: the idea that data written to magnetic media, such as hard disk drives, can be recovered even if overwritten, due to a quirk in the way hard drives write and read data.
Some of this notion stems from the fact that when a drive's head seeks to a given spot, it does not always seek to the exact same spot. Therefore data written to the same track might exist in a number of side-by-side iterations. So if you want to guarantee the erasure of a piece of data from a hard disk drive, you need to erase it many times over.
Scrub that disk!This notion spurred the creation of many data-erasure products that write randomly generated data to a file or a given piece of media, and use multiple iterations of the random-erase cycle to ensure the complete destruction of data. The more erase cycles, of course, the longer the process takes. The full implementation of Department of Defense's own 5220-22.M standard requires seven discrete passes. Imagine doing seven discrete full-surface formats of a hard disk drive and you'll have some idea of how tedious this is.
The idea that "erased" data wasn't really erased seemed plausible, but admittedly only because I hadn't solicited any second opinions about the matter. Is there any evidence supporting the hypothesis that to completely erase a drive, you must erase it multiple times?
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