Security Basics mailing list archives

Re: Interesting One


From: "Carlos ." <s0lrac () hotmail com>
Date: Wed, 30 Oct 2002 16:19:31 +0000






I fully agree with Mr. John Orr here and I find it particularly interesting that he works in a bank because I've heard ( my c++ teacher ) that some banks have to overwrite with zeros 3 or 4 times all of their HDs just to be sure there was nothing left on the drive. Maybe he was wring but that's probably because of the residual magnetic field left on the area as John said below. But if your FAST guy can read up to 30 times after writing, well he sound a little bit weird to me or maybe the technology he uses is really precise ( elaborated , high-tech )
Please excuse my poor written english ...

Anyways, that is my opinion, based on no years of experience and no good knowledge of physics.

ha....




From: "John Orr" <JOrr () austinbank com>
To: Subject: Re: Interesting One
Date: Tue, 29 Oct 2002 12:15:22 -0600

  Personally, I think he is full of... hot air.

Bits are either "on" or "off", "1" or "0". If you change that pattern (i.e. write over the same data area with a different sequence of bits), then the previous state of that field would not be determinable. Granted, there may be some residual magnetic field left on a particular area that is now "0" that had been "1", but the converse would not be true. There would be no residual field to read on an area that is now "1" that had been "0".

  Sounds like sales fluff to me.

Anyway, that is my opinion, based on years of experience and a good knowledge of physics.

-John

--------------------------------------
John Orr
VP/CIO
Austin Bank
903.759.3828 x2113
903.297.3094 fax
jorr () austinbank com

>>> "Dave Adams" <dadams () johncrowley co uk> 10/28/02 04:06PM >>>
Greetings Folks,

I had an interesting conversation today with someone from FAST
(Federation
Against Software Theft) They pretend not to be a snitch wing of the BSA.
Anyway, to get to the point, the guy that came to see me said that their
forensics guys could read data off a hard drive that had been written
over
up to thirty times. I find this very hard to believe and told him I
thought
he was mistaken but the guy was adamant that it could be done. My
question
is, does anyone have any views on this, or, can anyone point me to a
source
of information where I can get the facts on exactly how much data can be
retrieved off a hard drive and under what conditions etc etc.

Thanks

Dave Adams



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