Re: Fw- Laptop Security Ale

From: Bob Erck (
Date: Mon Apr 15 1996 - 14:49:51 EDT

Bob's reply to...
       RE>>Fw: Laptop Security Alert

I'm not aware that x-ray machines generate any magnetic fields. X-rays are
generated when electrons from a thermionic filament are accelerated to tens of
keV, and slam into a metal target (Bremsstrahling radiation). This could
conceivably damage electronics. In contrast, portal monitors must generate an
electromagnetic field of some sort to interact with the metal items on a

The experts

There is a lot of misinformation about what can and can't be safely
passed through the airport x-ray machines and the metal detectors.

ASA 400 film, when passed through the airport x-ray machines, gets
fogged... ASA 100 film is probably much more resistant. Nevertheless, film
should not be sent through the airport x-ray machines.

Can airport X-ray machines damage floppy disks, magnetic tapes, and
portable computers? Probably not. I would be more worried about the
metal detector than the X-ray machine. If the magnetic field is set
strong enough, walking through with a floppy diskette, computer tape,
cassette tape, or video tape can erase the tape. Although there have
been a few unsubstantiated reports of portable computers being damaged
by X-ray machines, it is unclear whether the X-ray machines were
responsible. Given the flimsy construction of early notebooks, and the
roughness inherent in any kind of transportation, whether by plane,
car, or train, it's likely that they wouldn't have survived the trip
even if they hadn't been passed through the X-ray machine. So what do
we know?
   + A Mayo Clinic study says X-ray machines don't damage floppy disks.
   + The Apple Powerbook manual specificly states that the machine
      should not be passed through airport X-ray machines. The
      Powerbook Companion, on the other hand, states that X-rays don't
      harm the powerbook.
Given that most airports are willing to hand-check computer equipment
and magnetic media, it's probably best to keep them clear of *both*
the metal detector and X-ray machine, just in case.
Do not rest your film or notebook on top of the x-ray machine -- they
aren't as well shielded as they could, especially on top.
Unless you rub your wallet along the coils of the metal detector, and
the field strength is set very high, walking through is unlikely to
wipe the magnetic strip on your credit cards.
Date: 4/15/96 12:00
To: Bob Erck
From: Nichael Lynn Cramer
At 9:59 AM 4/15/96, Bruce Terry wrote:
>Our systems manager forwarded the following warning to all of us at the
>College of Biblical and Family Studies here and I thought it worthy of
>with all of you. I am still wondering about the wisdom of putting a laptop
>through an X-ray machine anyway. Don't X-rays destroy the data on hard disks
>as well as floppies?

Whatever the effect of Xrays per se, the real problem comes from the rather
powerful magnetic fields that such devices produce.

In short never put a laptop or other devices containing magnetic media
(e.g. floppies, computer tapes, etc) through the X-ray machine. Nor, for
that matter should you carry them through the metal detector.

I've never had any problem with simply handing these devices directly to
the guard. She is then free to hand-inspect the device if she so wishes.
In any case she's been in this position a zillion times before and it
should come as no surprise to her.

Nichael __ Be as passersby -- IC

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Date: Mon, 15 Apr 1996 12:15:23 -0400
To: Bruce Terry <>,
From: Nichael Lynn Cramer <>
Subject: Re: Fw: Laptop Security Alert

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