Recovering overwritten data - can software alone do it?

[kythe]

There are lots of considerations. The bottom line, though, is that data overwritten is pretty much unrecoverable by ANY means, episodes of "NCIS" notwithstanding.

The trick is to actually overwrite it. There are some very good tools out there (e.g. DBAN, Eraser) that will do this. As far as I know, only the Host Protected Area on a disk is beyond such overwriting. A normal format, even a low-level one, might not do the job.

There have been rumors of more exotic methods of data recovery post-overwriting (they involve imaging the platters with scanning microscopes and/or analyzing the raw signal output from the read heads), but actual attempts to do this by researchers have usually only succeeded under some pretty strict assumptions, such as already knowing the data to be recovered, knowing the overwrite pattern and only one overwrite pass.

Whenever I want to start fresh on a drive or take it out of commission permanently, I always start with DBAN.