[IP] Re: a comment on "Phones studied as attack detector"

[David Farber <dave@farber.net>]

Begin forwarded message:

From: EEkid@aol.com
Date: May 13, 2007 6:47:52 PM EDT
To: dave@farber.net
Subject: Re: [IP] a comment on "Phones studied as attack detector"

I can see it now, some poor soul has a nuclear stress test or a  
nuclear thyroid treatment and a day later the DHS guys kick in their  
door thinking they're building a dirty bomb...    : )

There are so many potential false triggers from an array of chemical,  
biological or nuclear sources in the workplace of many government,  
industry, research or medical facilities that this whole idea seems  
nearly impossible to implement in the field.

Can you envision, a "no fly" list or "no travel" list based on  
repeated triggers of cellphone sensors?  Half the researchers and  
medical folk in the country would be on it.  Not to mention a long  
list of government employees.

My workplace has over two tons of uranium and numerous other nuclear  
sources, not to mention a staggering array of chemicals.  Half the  
employees I've seen seem to have a cell phone in their possession  
most of the time.

This can't possibly work as planned...

Jerry


In a message dated 5/12/2007 8:33:48 PM Eastern Daylight Time,  
dave@farber.net writes:

Begin forwarded message:

From: Valdis.Kletnieks@vt.edu
Date: May 8, 2007 3:58:23 PM EDT
To: dave@farber.net
Cc: ip@v2.listbox.com
Subject: Re: [IP] a comment on "Phones studied as attack detector"

On Tue, 08 May 2007 11:21:52 EDT, David Farber said:
> Detectors for bio events are notoriously flaky. They see false
> posoitives in  the 3-4% for mass deployed units. Consider if the
> False Positive of the cell phone detector was even 1%. The noise
> would be overwhelming.

Even if they get the FP rate down to 0.01%, you still hita problem -
statisticians call it the 'base rate fallacy'.  Floyd Rumin discussed it
well here: http://www.lewrockwell.com/orig7/rudmin1.html in the
context of
NSA data mining of phone calls and e-mail to look for terrorists.

Basically - you can't use data mining to find something very rare,
because
the false positives *will* drown you unless you have an insanely good
tool
to do the good/bad classification.

And even after all that, the terrorists can twist it to their
advantage...

Consider a terrorist cell that learns how to game the system and cause
false positives at will - the 395th time they have to clear a major
sports
stadium in the middle of a game, or close down the New York subway
system,
they'll give up on it.  Of course, at that point, the terrorists have
a 2-for-1 special on the advantage:

1) They'll have a detailed understanding of exactly what the response
time
and capabilities of responding units are.

2) The 396th time....




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