| It would be nice if you quoted some reputable source or research when making such bold claims. Who are the people that can recover more than 1 rewrite easily from a modern hard disk drive, do you have any URLs at hand? You could check Peter Gutmann's research titled "Secure Deletion of Data from Magnetic and Solid-State Memory" [1] from 1996 which is one of the original sources for "35-cycle erase" [2]. In this paper he states that it is possible to recover the data using a specialized microscopy equipment (using Magnetic Force Microscopy or MF Scanning Tunneling Microscopy techniques). These techniques are only applicable for mediums with a much lower magnetic density and much simpler encoding than are used these days (eg. RLL encodings like MFM, PRML, etc.). How did you arrive at the number 50? In the epilogue of his paper Gutmann states: In fact performing the full 35-pass overwrite is pointless for any drive since it targets a blend of scenarios involving all types of (normally-used) encoding technology, which covers everything back to 30+-year-old MFM methods (if you don't understand that statement, re-read the paper). If you're using a drive which uses encoding technology X, you only need to perform the passes specific to X, and you never need to perform all 35 passes. tl;dr: overwriting 35 times is a pointless waste of time and is one of the popular myths that refuses to die. Using shred under GNU/Linux or DBAN to overwrite with some random data is more than sufficient for our purposes. [1]: https://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html [2]: http://en.wikipedia.org/wiki/Gutmann_method |