Those who seek to do premeditated harm will almost always attack through weaknesses in the system. Concentrating on the big-10 airports won't be very effective in increasing the security of the system as a whole.

It's a tough problem (see below), but treating everyone as a potential suspect isn't going to make the system safer at an acceptable cost. I'm not advocating profiling - I'm advocating real methods that increase system security (many of which have already been implemented - stronger cabin doors, agents on planes, etc.).

Basically, by the time the "evil-doers" are at the airport, it's too late (as illustrated by the recent events in [link|http://news.bbc.co.uk/2/hi/uk_news/scotland/6257194.stm|Glasgow]). Physical security at airports is important, but attempting to divine intentions of people in a queue there is far too late in the process.

[link|http://www.addictinggames.com/airportsecurity.html|Airport Security] Shockwave game. :-/

Of course, [link|http://www.schneier.com/essay-163.html|data mining has lots of problems], too:

[...]

Used properly, data mining is a great tool. As a result of data mining, AT&T reduces the costs of cell phone fraud, Amazon.com shows me books I might want to buy, and Google shows me advertising I'm more likely to be interested in. But it only works when there's (1) a reasonable percentage of attacks per year, (2) a well-defined profile to search for, and (3) and a low cost of false alarms.

[...]

Terrorist plots are different. First, attacks are very rare. This means that even very accurate systems will be so flooded with false alarms that they will be useless: millions of false alarms for every one real attack, even assuming unrealistically accurate systems.

Let's look at some numbers. Assume an unrealistically optimistic system with a 1-in-100 false positive rate (99% accurate), and a 1-in-1,000 false negative rate (99.9% accurate). That is, while it will mistakenly classify something innocent as a terrorist plot one in a hundred times, it will only miss a real terrorist plot one in a thousand times. Assume one billion possible "plots" to sift through per year, about four per American citizen, and that there is one actual terrorist plot per year.

Even this unrealistically accurate system will generate 10 million false alarms for every real terrorist plot it uncovers. Every day of every year, the police will have to investigate 270,000 potential plots in order to find the one real terrorist plot per month.

[...]

FWIW.

Cheers,
Scott.