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Securely erasing all data from a hard drive
I (full) formatted my external hard drive. Now, before giving it to someone else is there anyway to make sure there is no way to retrieve data using some of these recovery software's?
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1Which operating system ?– KarolosFeb 11, 2012 at 21:25
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If it wasn't being given away, I woulda said to get a shotgun for it...– Canadian LukeFeb 11, 2012 at 21:27
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5 Answers
Use Eraser - this free utility will overwrite your entire drive with your choice of patterns - up to and including the 35 pass Guttmann.
Use Darik's boot and nuke: www.dban.org/ - It's a bootable disk that will run on any system and totally delete selected hard drives in/attached to the system. Just make sure you are deleting the right drive if you have more than one.
Reformatting the drive will effectively mean that a typical user who just wants to use the drive won't be able to access the files.
However, there is software available that can recover data from such drives. How much data they get back depends on what's been done to the drive since it was formatted. Overwriting the drive with new meaningless data achieves this.
This article goes into more details and lists some of the software you can use to achieve this. As it says you need to overwrite the data several times to ensure it's completely irrecoverable:
The Gutmann Method
Based on Peter Gutmann's paper "Secure Deletion of Data from Magnetic and Solid-State Memory", this method provides the best security. Data is overwritten 35 times with carefully selected patterns, which makes it unrecoverable. Unfortunately, it also makes it time consuming.
US DoD 5220-22.M
Based on the United States Department of Defense recommendation 5220-22.M, this method overwrites the data seven times. While less secure than the Gutmann method, it is faster.
However, other evidence shows that this might well be overkill and that a single pass of pseudo random data is enough.
The article ends with a technique to ensure that your data remains deleted forever:
- Remove the hard disk from the computer
- Unscrew the casing, exposing the disks
- Smash them to smithereens
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335 passes are not needed (even Gutmann himself states so). In fact, you very likely are okay with just one psuedorandom pass. See also this question. Feb 11, 2012 at 21:54
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1And that article is somehow infallible? Gutmann himself states, as I referenced above, "it will have no more effect than a simple scrubbing with random data". Feb 11, 2012 at 22:03
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Data may be recoverable if you simply formatted or 0'd the drive.
In linux use srm, included in the secure-delete package.
In OS X, cli srm is available, but disk utility may be more convenient and has the same effect.
On Windows, you can run diskpart and use the clean all command. This will zero out the drive.
answered Feb 11, 2012 at 21:21
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Will it write zero's to the drive or will it just nuke the partitioning information?– HennesDec 10, 2015 at 13:04