FC: Data miner replies to Politech, says TIA can ID terrorists

[Declan McCullagh <declan () well com>]

Previous Politech message:
"What's so bad about Total Information Awareness? by Ben Brunk"
http://www.politechbot.com/p-04234.html

Gregory Piatetsky-Shapiro's bio is here:
http://www.kdnuggets.com/gps.html

---

From: "Braunberg, Andrew" <Abraunberg () currentanalysis com>
To: "'Declan McCullagh'" <declan () well com>
Cc: "'KDnuggets Editor'" <editor () kdnuggets com>
Subject: FW: Can TIA work or how can you separate bad coins from good ones? 
By repetition
Date: Tue, 10 Dec 2002 14:52:45 -0500

Declan,
    I follow the data mining industry fairly closely and am also a reader 
of Politech. I passed on Ben's TIA concerns to Gregory Piatetsky-Shapiro, a 
well known expert in the industry. His response follows. He is happy to 
have you post it to Politech if you desire.

Best,

Andrew Braunberg
Senior Analyst,
Data Warehousing
Current Analysis

abraunberg () currentanalysis com
912/236-6912

"Never express yourself more clearly than you think."
--Niels Bohr


-----Original Message-----
From: KDnuggets Editor [mailto:editor () kdnuggets com]
Sent: Tuesday, December 10, 2002 12:16 PM
To: Braunberg, Andrew
Cc: editor () kdnuggets com; Farhad Manjoo
Subject: Can TIA work or how can you separate bad coins from good ones? By 
repetition

Andrew,

        thanks for the note.

There are serious questions about whether TIA can work and how much privacy 
it will erode.

There is no doubt that TIA will produce some false positives.

However, the statistical analysis given by Ben Brunk is very naive and 
shows lack of understanding how the system might work. Data mining as a 
useful technique has not been debunked -- all large companies are using it 
every day.

The whole idea of finding patterns is that with enough history and 
repetition the suspicious patterns will stand out, despite noise and errors.

Imagine that you have a thousand coins and that two of them are crooked 
(i.e. probability

of heads is not half but 1/4)

If you flip each coin once, you cannot determine which one is crooked.

If you flip each coin a twenty times, crooked coins will have about 3-7 
heads, but a few dozen "false positive" honest coins will also have about 7 
heads.

If you flip each coin a thousand times, crooked coins will have about 230 - 
270 heads, while honest coins will have 480 to 520 heads. So with a rule --

        number of heads < 350

you will catch all crooked coins and no honest coins.

How many times you will need to flip each coin to find at least one crooked 
coin?

That depends on the level certainty you want, the number of crooked coins, and

how crooked is each coin.

Applying this to terrorists, if there is ONE terrorist that does ONE thing 
that is a LITTLE suspicious, no system cannot find it.

However, if there are MANY terrorists that do MANY things that are STRONGLY 
suspicious, the system will find them.

How many is needed? We don't know, but that is one of the questions that 
TIA wants to investigate.

Of course the real system will be using much more complex reasoning than 
what I presented above.

Gregory Piatetsky-Shapiro

President, KDnuggets

The Source of Expertise in

Data Mining and Knowledge Discovery

At 08:30 AM 12/10/2002 -0500, you wrote:

>>>>



Gregory,

Good morning. I thought you would find the attached analysis of TIA 
interesting. It comes from the Politech mailing list which is moderated by 
Declan McCullagh, who was until recently Washington bureau chief of Wired 
and is now at Cnet. The list is very well respected in the civil liberties 
community. I thought you might have some unique insight or might wish to 
pass the discussion on to your wider readership.

Best Regards,

Andrew Braunberg 




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