Can You Ever Really Erase a Computer File?

[Dimandja]

http://slate.msn.com/id/2121745/

 

[sleipnir214]

I'm not suprised by the recoverability of data. I read a couple of years ago an article that said the U.S. Department of Defense always physically shreds hard drives to ensure their unusability.


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TANSTAAFL!!

 

[eyec]

you can 99.99999% erase a computer. however, after erasing them you should write a series of characters over the entire hard drive; such as BBBBBBBBBB or something along that line using a bit by bit write process.

that way you have pretty much accounted for destroying that .000001%.

finally, not all delete/erase programs are created equal!

 

[lgarner]

One thing that overwriting files doesn't account for is the sloppiness of the heads when they write data. I read a similar article some time ago, which indicated that bits won't necessarily be written in exactly the same place twice.

Picture yourself painting a groove with a paintbrush, by hand. A little paint will get on the sides, which might not be covered in the next pass. These little "splashes" can provide information to the recovery agent.

 

[needcoffee]

If you are that concerned with erasing your data buy a high power degausser. Use it after you perform your overwrite, low-level format, etc. Then format and overwrite again. Repeat until your paranioa or security policy is satisfied.

If you are not reusing the disks at your company why not just destroy them. It's a lot cheaper than the time and effort involved above. Pull out the plattens and dunk them in some acid until disolved. Another option is to send them through a metal shredder like the US DOD.

needcoffee

 

[DJ2liveUK]

I have come across some HDD where the platters are made of glass, so hitting them with a hammer will destroy ALL data (unless you are particularly good at gluing things back together).

 

[sleipnir214]

This has been a known issue for quite some time. It's why the U.S. Department of Defense removes hard-drives from computers and runs the drives through a metal shredder.

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TANSTAAFL!!

 

[netmanrick]

If you use a degausser on a disc drive,it will be rendered useless.
There is a servo track on the platter;when it's damaged or erased,the HDA is useless.
Use a DOD-approved eraser,like SHRED. It writes enough bit patterns so that any recovery/forensic software yields garbage.
Back in the days of my CAD/CAM field service,NASA would attach a little C-4 to the HDA's to render them useless.

Rick Harris
SC Dept of Motor Vehicles
Network Operations

 

[DrJavaJoe]

I prefer the C-4 method myself, lots and lots of C-4 the more the merrier.


Two strings walk into a bar. The first string says to the bartender: 'Bartender, I'll have a beer. u.5n$x5t?*&4ru!2[sACC~ErJ'. The second string says: 'Pardon my friend, he isn't NULL terminated'.

 

[sleipnir214]

You know, thermite is quieter and can be created in your kitchen.

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TANSTAAFL!!

 

[damber]

For those of us that want to keep our HDD for other uses.. maybe for sale etc, or you just want to ensure nobody ever retrieves that revealing christmas party photo of you.. try this util:

http://dban.sourceforge.net/

Very useful and probably as secure as you can get without physically destroying the drive.

There are several algorithms it uses, including the American DoD 5220-22.M, an algorithm designed by Peter Gutmann and a PRNG (Mersenne Twister) Stream (which along with the Gutmann wipe is the most secure).

And this can take a while to run - especially if you're really paranoid and set the iterations (rounds) to a ridiculously high number...

But I think the most fun solution is the c-4...

A smile is worth a thousand kind words. So smile, it's easy!

 

[Trevoke]

low-level format.
The guy who said to write a character through the entire drive is right.
dd if=/dev/0 of=/dev/hda

for Linux will get the job done.

-Haben sie fosforos?
-No tiengo caballero, but I have un briquet.

 

[needcoffee]

I heard a few years ago that their was enough trace field strength left on a disk to pull 'deleted' information from under 7 layers of formatting and rewrite. They may be able to get down even lower today. If you are reusing the drives within your enterprise a couple of runs with DBAN and a low-level format will suffice for my paronia. I [red]do not[/red] let drives retire in machines leaving our control. They are summarily executed by whatever method I feel like using that day. Some favorites are metal grinders, acid, shredders, and explosives. If you have a truley wretched machine you want to remember you can store the dusk in an urn as a future warning to other misbehaving machines.

Almost every workstation in our enterprise contains ePHI and we can't take the risk of information exposure. It is a number of magnitudes cheaper to purchase replacement drives than face a lawsuit.

needcoffee

 

[compuveg]

The linked article stated 35 wipes was what some group did. I think that if your data is really that sensitive, you can probably afford glass platter hard drives like mentioned earlier in the thread.

What I do for bad hard drives at my workplace is to drill straight through the platter area 2 different times, then give it to the cmpany that does our EPA certified tech disposal. They are supposed to physically shred the drives, too, but unless you see it go into the shredder there's no guarantee that it has been done.