Use something like DBAN [1] and forget about it.
(Happy to be corrected)
[1]: http://www.dban.org/
for ATA disk drives manufactured after 2001
(over 15 GB) clearing by overwriting the media once is adequate to protect the media from
both keyboard and laboratory attack.
Found that while looking up the DoD standard, interesting stuff - thanks!
There was one study a long time ago where a few bits were recovered with some accuracy with an electron microscope, but it was from a really old hard drive with a much lower density than current ones.
Those overwriting regulations are just in case such technology might get invented in the future.
1. Secure Erase will only take a few seconds.
2. DBAN is going to shorten the life of the drive.
3. Yes, recovering data that has been overwritten is unlikely. However, DBAN is likely to not write over the data in the first place. It has no control over where the data is written. That's handled by the SSD controller. DBAN will only think it wrote zeros over the entire drive, while not actually doing so.
If you're just an ordinary Joe/Joelle:
- write 'all zeros' to the whole drive
If you've been committing small time crime:
- (the above+) write 'all ones' to the whole drive
If you're a big time crime boss (say Escobar level):
- (the above+) disassemble the drive
If you're either Edward Snowden or Julian Assange:
- (the above+) smash controller to bits, sandpaper platters
If you're Osama Bin Ladens cleaning lady:
- (the above+) melt down the drive elements
Imho anything above except for step (1) is overkill.
If it is a Windows machine and you are trying to leave Windows in-place (not recommend) you can at least delete your user account, empty the trash can, and then run a program like SDelete - http://technet.microsoft.com/en-us/sysinternals/bb897443.asp...
"We" incinerated hard drives at EOL.
"We" did that for a reason. Anything short of destruction means the data can be recovered if somebody has enough will.
shred is a Unix command that can be used to securely delete
files and devices so that they can be recovered only with
great difficulty with specialised hardware, if at all. It
is a part of GNU Core Utilities.http://gizmodo.com/5494427/leave-no-trace-how-to-completely-...
http://www.cnet.com/how-to/how-to-securely-erase-an-ssd-driv...
Do it 50 times, then it should be safe (if your paranoid, melt the drive though)
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