running Magnet/dist...
 
Notifications
Clear all

running Magnet/distorting HDD contents: urband legend?

williamsonn
(@williamsonn)
Member

I have read anywhere that running a potent magnet over a hard drive distorts its magnetics contents….I am not at all an expert, but, it sounds me like an urban legend. Does that affirmation about the magnet make any sense in reality?

Quote
Topic starter Posted : 14/01/2013 4:58 pm
hc4n6
(@hc4n6)
New Member

We use a Degausser in my workplace for permanently wiping hard drives.

http//en.wikipedia.org/wiki/Degaussing

So no, it is not an urban legend. If you place a credit card too close to a magnetic source it is likely that it won't work afterwards.

ReplyQuote
Posted : 14/01/2013 5:38 pm
ThePM
(@thepm)
Active Member

You have to be careful with degaussing. This was true when hard drives were using longitudal recording. However, since newer hard drives use perpendicular recording, degaussers are not 100% reliable. Since those drives require a lot more magnetic force to completely degauss a drive, this force cannot always be applied by a table-top degausser.

In 2012, NIST drafted a revision of their "Guidelines for Media Sanitization" guide (http//csrc.nist.gov/publications/drafts/800-88-rev1/sp800_88_r1_draft.pdf) and the following text can be found

"Destructive techniques for some media types may become more difficult or impossible to apply in the future. Traditional techniques such as degaussing (for magnetic media) become more complicated as magnetic media evolves, because some emerging variations of magnetic recording technologies incorporate media with higher coercivity (magnetic force). As a result, existing degaussers may not have sufficient force to effectively degauss such media."

I was not aware of this until last September when I attended a hard drive repair and recovery course and the instructor spoke with a guy at NIST who shared this info with him. The instructor said that with recent hard drives, it is possible that degaussing could only corrupt the System Area, preventing the drive from initializing and tricking the user into thinking that the drive has been sanitized. But some "simple" System Area fixes could allow access to user data.

NIST says that to know if a degausser is effective for a specific drive, it would help to know the magnetic force used by a drive to write the data and compare it to the magnetic force that can be deployed by the degausser. Unfortunately, the magnetic force used by the drive is generally not mentioned in the tech specs on manufacturers websites.

BTW, I have not tried this myself but I though it might be worth to know.

ReplyQuote
Posted : 14/01/2013 7:42 pm
hc4n6
(@hc4n6)
New Member

You have to be careful with degaussing. This was true when hard drives were using longitudal recording. However, since newer hard drives use perpendicular recording, degaussers are not 100% reliable. Since those drives require a lot more magnetic force to completely degauss a drive, this force cannot always be applied by a table-top degausser.

That is very interesting, I was not aware of it either. It is time to perform some tests. mrgreen

ReplyQuote
Posted : 14/01/2013 8:11 pm
jaclaz
(@jaclaz)
Community Legend

If I get it right the issue is that the so-called "gray areas" or servo control zones that may be affected "just enough" to make the rest of data unreadable (to the actual proprietor/disposer of the disk) but recoverable by re-formatting at low-level and/or repair those areas (by a very knowledgeable intruder/terrorist/whatever).

It is happening in practice what till now was only "philosophical" issue, using a method that you have no "real way" to check if worked is - paradoxically - less secure than an hypothetically less secure method that you have ways to check it worked.

Imagine that you could not burn or shred papers.
When you have to destroy for safety reason a folder of (say) 100 sheets you could have only two ways

  1. going over each page one by one and cover each line with some felt tip black pens
  2. immerge the whole folder "as is" into a can of glue for a few minutes and them let it dry
  3. [/listo]

    The first method allows you to check that each and every line was actually covered but someone could come out with a technique to read below the ink (no matter how many passes you do with the felt tip pen wink ) at least some words here and there.
    The second method does not allow "inspection" of the result, IF it works, it works allright, but you have no way to check that each page is properly glued to the one before, so IF it doesn't work you are potentially leaking much bigger chunks of data 😯 .

    I would always personally prefer the first method from a philosophical standpoint, but breaking the platters into pieces and sending those pieces to random addresses (in China or elsewhere) starts making some sense…..

    jaclaz

ReplyQuote
Posted : 15/01/2013 2:11 pm
williamsonn
(@williamsonn)
Member

Then, I see it is not an urban legend wink although, mostly, only useful in old drives.
However, this destructive effect we are talking about is only using a professianal degaussing device, or also using common magnets(i.e. those in speakers, and other electronic devices)

By the way for an non expert like me how is possible to easily know if a hard drive uses or not perperdincular recording brand, model etc say anything?

ReplyQuote
Topic starter Posted : 15/01/2013 5:07 pm
jaclaz
(@jaclaz)
Community Legend

Then, I see it is not an urban legend wink although, mostly, only useful in old drives.

No, not really.
The "principle" is still fully effective, it may depend on the force of the magnet/degaussing device.

However, this destructive effect we are talking about is only using a professianal degaussing device, or also using common magnets(i.e. those in speakers, and other electronic devices)

Again, not really.
There isn't a definition of "common" magnets, nor for "other electronic devices".

Read this thread
http//www.forensicfocus.com/Forums/viewtopic/t=7640/

An "average" professional degaussing device is essentially an electrical machine that will convert something in the range of 230 V ac 10÷15 A (i.e. between 2,300 and 3,500 W approximately) of electricity into a rather focused magnetic field, let's say covering a surface of 15 x 30 cm.
I would presume that any electro-magnet of similar power (possibly coupled with a pulse generator) would produce the same amount of gauss.

By the way for an non expert like me how is possible to easily know if a hard drive uses or not perperdincular recording brand, model etc say anything?

You can know the size of the hard disk (capacity) and (most often, but not always-always, there are known issues with at least a Seagate model that has the SAME model number but that actually ships with a different number of platters and different motor) the number of platters.
You do some math and you find the (very approximated) areal density expected for the platter surface.
http//en.wikipedia.org/wiki/Perpendicular_recording

A rule of the thumb is year of production, anything before 2006 is NOT perpendicular recording, anything after it, if bigger than (say) 160 Gb, it is likely a perpendicular recording disk drive (talking of 3.5" hard disks, obviously lower capacity if 2.5").

jaclaz

ReplyQuote
Posted : 15/01/2013 7:20 pm
Wardy
(@wardy)
Active Member

I've managed to render a perpendicular drive useless with some very powerful rare earth magnets.

ReplyQuote
Posted : 15/01/2013 7:24 pm
jaclaz
(@jaclaz)
Community Legend

I've managed to render a perpendicular drive useless with some very powerful rare earth magnets.

Yep ) , but "useless" does not equate necessarily to "securely wiped", as per PM_SQ previous post, and "rare earth magnets" is not particularly descriptive either, examples wink
http//www.rare-earth-magnets.com/images/product/medium/nsn0621_2_.jpg
http//www.earthchain.com/images/ez-lift6.jpg

jaclaz

ReplyQuote
Posted : 15/01/2013 9:23 pm
jhup
 jhup
(@jhup)
Community Legend

Last week, I have also managed to render a perpendicular drive useless with some very powerful Windows 8.

mrgreen

ReplyQuote
Posted : 16/01/2013 10:46 pm
jaclaz
(@jaclaz)
Community Legend

Last week, I have also managed to render a perpendicular drive useless with some very powerful Windows 8.

Well, the good news are that there is a rather cheap cure for it wink
http//www.startisback.com/

More seriously, set apart the NCI (Nameless Crap Interface) Windows 8 is not that much different or "worse" than 7.

I did a few tests on VM's, and it seemed a tiny bit faster (or only a tadbit more responsive) then comparable 7 installs.

However, I still have a few spares of the sticks I had made for NOT touching Vista (and will use for 8)
http//www.msfn.org/board/topic/125258-nlite-and-microxp/page__view__findpost__p__807225
should you need one, just let me know.

jaclaz

ReplyQuote
Posted : 17/01/2013 12:35 am
Share:
Share to...