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March 1997

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From:
[log in to unmask] (Doug McKean)
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Date:
Tue, 11 Mar 1997 16:42:37 -0500
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Hugh J. Rundle wrote:

> I am in search of material to determine the effects EMI/RFI/H-field and
> other invisible environmental influences have on data/computer media.
> Is this a real threat or a perception that data can easily be erased?
> I am also interested in products you know of on the market that protect
> media from loss by such disaster.
> 
> Thank you for you assistance.
> 
> Best regards ... Hugh Rundle
>                  SafeSupplies Inc.
>                  http://www.safesupplies.com
>                  [log in to unmask]


It's very real. I don't intend to sound gloom and doom BUT 
any magnetic media that you depend upon for data storage is 
at risk. Two main things of importance are strength of the 
field and the length of exposure time. 

Any time current flows through a wire, a magnetic field is 
set up around the wire. Alot of current -> alot of magnetic 
field. Plain and simple. What's not so simple is how many 
different ways this can happen.

Some "Real Life" examples: 

An engineering friend of mine would take work home. 
After a long laborous project he came to work completely 
frustrated. "Those damn disks", he said, "they always go 
bad!!!"  After some careful questioning I found out he 
would put his disks on speakers to his stereo next to 
the pc. 

What does that have to do with anything?  

There are some big magnets inside speakers to make them 
work.  Not only that, when the stereo is played, current 
drives the magnets in the speakers. They establish a 
magnetic field. Viola! Instant eraser. 

Did it happen in one night?  

No.  

But continued exposure will allow it to happen. 

How about those magnetic paperclip holders I've seen 
on people's desks? If you rely on magnetic media for 
your job, throw them away, and state a company edict 
those in violation will be whipped. 

Leaving magnetic media around your video tube for a pc 
will spell death to data.  May not happen now, may not 
happen tomorrow, but I guarantee it has already started 
happening. 

Alot of this can be avoided by proper "handling" and "storage". 

Sending disks through the mail can be dangerous. If they are 
exposed to a strong scanner, they can easily be erased. Best to 
get special envelopes for that purpose. Also, going through 
the airport with disks can be dangerous. The scanners for 
luggage and the wands for weapons can erase stuff. 

Keep in mind that full erasure is not neccesary. 
It only takes a couple of bits to ruin your whole day. 

What's worse is if you use compression for data storage, 
the compression techniques TAKE OUT data redundancy. So 
missing bits is even more critical on compressed files 
like PKZIP to name just one. 

I think I've said enough. 

Regards, Doug

************************************************************
  -------------------------------------------------------
  The comments and opinions stated herein are mine alone,
          and do not reflect those of my employer.       
  -------------------------------------------------------
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