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View Full Version : Does degaussing still happen?



Ttaylor394
10-28-2014, 10:44 PM
I remember back on my parents Gateway Millennium edition PC the monitor had a degaussing button. Never really had a use for it or understood what that meant until college.
Now I work in radiology and have a more than basic knowledge of MRI units.
I have been wondering-what are the standard ways to wipe clean a hard drive?
I always assumed a drive would be plugged into what ever peripheral it needed and somebody would hit reformat on a home base computer. I come to learn there are certain levels of security- just in OS X we can select an option that will take 15 hours or something to write a zillions zeros on your hard drive. Or just 30 seconds and then it's "empty" again but with out it really being blank.
Wouldn't a very strong magnetic field do the trick much faster and just as "secure"?
The Magnet in my hospital is average at 1.5 or 2.0 tesla. From what Google showed me that's about average for degaussing magnets available for purchase. If you have enough current/amps there isn't really a limit to what people can push through a magnet. Some research hospitals have 10 T magnets. And from an episode of myth busters I think there are magnets up near 45 T
I get that it may not be cost efficient to have a liquid helium super cooled magnet for a business to wipe clean hard drives. But wouldn't it be more efficient time wise?
Sorry for rambling.

chscag
10-28-2014, 11:14 PM
For your questioning mind... ;) The US government does not reuse a hard drive once it stored classified data. They first use a wiping routine (similar to what Disk Utility would do), they then degauss, and afterward completely destroy the drive.

The degaussing you referred to above on the "Cow Box" (Gateway) was to remove any magnetism on the surface of the CRT. Older style TV sets likewise had built in degaussing circuitry. Modern LCD displays are not subject to the same magnetic distortion and no longer need to be degaussed.

Ttaylor394
10-29-2014, 01:45 AM
At least there is something that uses redundancy inside the government that indeed-needs redundancy.

Exodist
10-29-2014, 02:30 AM
Degaussing removes the magnetic field that a CRT can pickup, basically grounding it out. On pretty much all modern Navy ships the entire ship has a degaussing system to prevent mines from being drawn to the ships hull. Plus other various reasons they likely wouldn't disclose. But when I was in the Navy most of the ships still used CRT monitors and we frequently through out the day would end up having to degauss the display to keep from looking at rainbows.

As far as hard drives I think Chscag meant secret/secure(RED) on those drives, as everything was rated as classified(GREEN). Every classified drive is reused in classified systems. But once it quits working it is then sent stuck to a large magnet and whipped. I think the IT department would even send the secure ones in for further cleansing. At least thats how the Navy did it. We used everything until it physically couldnt be fixed.

As far as data security, there is ways of completely removing data from your drive, but it consist of writting random data bits to the drive in hand many times over and over. I think it was up to 10 times for what the NSA recommends for standard security. IIRC.

McBie
10-29-2014, 03:32 AM
Degassing still happens in some organisations.
After that it is usually thrown into an oven and burnt beyond recognition :-)

Cheers ... McBie