"Zeroing out" HDD and security

A

ann0yanc3

Gawd
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Nov 27, 2004
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I know the 7-pass random data is the standard, but how can someone possibly get something from all 0's?
 
I'm not current on this so don't take this as having any athority behind it.

I belive in the past i had read that with the proper equiptment it is possible to look at data that was on the drive a few writes ago. so if some thing was over written say 3 time they could in theory read all 4 layers of writes.

7 passes of overwriting is intended to make it difficult enugh that the person trying to get the data will move on to another drive that may not have even been erased insted of taking the time/cost to get at your data, kind of like locking the doors on a POS car and parking next to a Corvette that has the top down.
 
Thrus said:
I'm not current on this so don't take this as having any athority behind it.

I belive in the past i had read that with the proper equiptment it is possible to look at data that was on the drive a few writes ago. so if some thing was over written say 3 time they could in theory read all 4 layers of writes.

7 passes of overwriting is intended to make it difficult enugh that the person trying to get the data will move on to another drive that may not have even been erased insted of taking the time/cost to get at your data, kind of like locking the doors on a POS car and parking next to a Corvette that has the top down.
Click to expand...

It takes a $100,000 piece of equipment to see what the state of a single bit might have been.

Any more than a single pass is a simple waste of time. There is absolutely no way anyone is going to be able to recover data after that using software.

http://www.h-online.com/security/Secure-deletion-a-single-overwrite-will-do-it--/news/112432
http://www.whitecanyon.com/newsletter-hard-drive-erase-multiple-overwrites.php
http://www.lawtechnews.com/r5/showkiosk.asp?listing_id=3107662
 
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I agree with ryan on that one is most likely plenty for protection. If you are disposing of a drive, then again there is always the drill press method if you are just junking the drive and want your data safe as well.

On the other hand what you do depends on if it is home or work and if work what your customers may want to be happy. if dealing with department of defence/military stuff 7 overwrites and a drill would probaly make them happy. if at home write it once as the guy in the trash that wants data will just go to the neighbors that didn't bother to even delete thier data.
 
Thrus said:
I agree with ryan on that one is most likely plenty for protection. If you are disposing of a drive, then again there is always the drill press method if you are just junking the drive and want your data safe as well.

On the other hand what you do depends on if it is home or work and if work what your customers may want to be happy. if dealing with department of defence/military stuff 7 overwrites and a drill would probaly make them happy. if at home write it once as the guy in the trash that wants data will just go to the neighbors that didn't bother to even delete thier data.
Click to expand...

There's no most likely about it. One pass of zeroing out every sector on the disk is going to render data unrecoverable. Advanced equipment might get a few random bits, but it will not get anything useable, not even so much as a single letter of your name.

Of course, making people happy often counters reality. So yeah, if you're boss is saying " I want this drive wiped 500 times using this random bit method" then you'd best do it.
 
i use file shredder and zero the drive after ive deleted the partition and reformatted if its something i plan to sell, if its junk a hammer and screw driver through the platters works great
 
CanadaOwnsJoo said:
i use file shredder and zero the drive after ive deleted the partition and reformatted if its something i plan to sell, if its junk a hammer and screw driver through the platters works great
Click to expand...

that sounds a bit excessive. zeroing out the drive is all that needs to be done.

For a junk drive that can't be zeroed, yeah, break the platters or destoy the heads. It's easy enough to find a control board and swap it out and have a working drive.
 
Your best bet for software level data destruction is to dd wipe the disk using linux/unix. Professional data recovery companies like Drive Savers won't accept drives that have been accidentally dd wiped because they aren't capable of retrieving the data (but won't admit it).
 
zero fill wipe, then dban on top... or to really chew up work time, zero fill wipe, trucrypt encryption, diskbench to fill drive w/ useless data, then dban to wipe it several times...
You know defense in depth? This is disk scrubbing in depth... is it excessive? Absolutely! is it unnecessary? most likely! does it kill time at work and make u look busy? Absolutely! and that makes it worthwhile...
 
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