The Problem of Identifying the Terrorists (Bad Guys) Quickly

by

Dr. Peter Chen

& Cyber Security Group

Computer Science Dept

LSU

Baton Rouge, LA 70803

Outline

• What is the Profiling Problem?

• Why is it so difficult?

• What are we doing about it?

What is the Profiling Problem?

In any population, …

there are bound to be bad guys:

there are bound to be bad guys:

Let’s meet some of them:

A bad guy

Another bad guy

Several bad guys

Looking more closely at each bad guy:

Bad guy 1

• black hair• beard/moustache

Bad guy 2

• well dressed• beard/moustache

Bad guy 3

• black hair• beard/moustache

Bad guy 4

• black hair• highly strung• skinny

Attributes of bad guys

• black hair

• beard/moustache

• well dressed

• skinny

“black hair”:

“beard/moustache”:

“well-dressed”:

“highly strung”:

“skinny”:

Using the fewest attributes to catch all the bad guys

• black hair

• beard/moustache

Unfortunately, in our population

…there are also good guys:

Looking more closely at each good guy:

Good guy 1

• beard/moustache

Good guy 2

• beard/moustache• well-dressed

Good guy 3

• well-dressed

Using the fewest attributes to catch all the bad guys …

• black hair

• beard/moustache

…also catches some good guys (casualties):

• black hair

• beard/moustache

…also catches some good guys (casualties):

• black hair

• beard/moustache

Goal: • Find the smallest number of attributes that will catch all the bad guys, but at the same time • Include as few casualties (good guys) as possible.

Some good guys are more important than others

Some bad guys are more important (to capture) than others

Goal (more ambitious):• Find the smallest number of attributes that will catch as many, and preferably the more important bad guys, but at the same time • Include as few, and preferably the less important good guys, as possible.

Why is the Profiling Problem so difficult?

Why can’t we just try all possible combinations of attributes, and

then pick the one that does best?

For, after all, computers are fast, aren’t they?

This problem is complex

• Computers are fast, but not for certain problems, the complexity of the problems will make the computation time grow exponentially. The Profiling (Bad Guy Risk Assessment) is such a problem

• Unfortunately, the Profiling Problem is one such problem:Adding one more bad guy, or one more attribute may make the problem take twice as long to solve.

• Also, adding one more attribute value (for example, adding a new value on possible hair color will increase significantly the computation time.

No use coming up with the best solution many

days/weeks/months after we are all dead and gone.

OK. How about a quick method to find a solution that close to the

best?

We have developed algorithms to solve this problem that do not take so long, yet produce very good results.

Summary

• In the Profiling Problem, we want to catch as many bad guys, especially the real bad ones, and do so by disturbing as few good ones, especially the important ones.

• The Profiling Problem takes too long to solve if we want perfect solutions. No one knows if we can get perfect solutions fast.

• We have develop a quick algorithm to find the solutions in a reasonably short time.

The End