The NYPD is using social network analysis to track possible homegrown terrorists. And it’s finding clusters in the social web.

Using the NYPD matrix, those officials say there are at least two dozen “clusters,” or “pockets,” of individuals in the region who are at various places along the path of radicalization.

This is being done through a community mapping model

Here’s the full NYPD Report. (pdf)

City Journal profiled the NYPD innovative Intelligence Division before, and I discussed it here.

So how does the Intel division do its work?

The purpose of the structure proposed by the NYPD is to create a tool enabling authorities to measure whether these “pockets” are moving from sanctioned activities toward violence.

The dense, 90-page NYPD analysis is the nation’s first full analysis of the potential for increased homegrown terror in the United States and the first to develop a matrix on which to plot the course of “unremarkable” people as they move toward the potential for violent action, multiple persons familiar with the report told ABC News.

Months in the drafting, the report makes use of a novel “cluster” model to determine where on the path from preradicalized and self-identification to indoctrination and jihad an individual and immediate peer group may be. As such, it is a valuable tool for assessing individuals that come to law enforcement’s attention and in making cogent arguments in court cases, sources who reviewed the report’s drafts told ABC News.

The threat comes from “Al-Qaedaism” rather than any formal organization. Lone individuals or small clusters will pick up a militant Salafi ideology and target hated groups. Since this is an Information War, monitoring the dissemination of ideas is more important than formal organizations. As such, the idea is to look at mosques, bookstores, and internet sites to see who will turn radical.

The NYPD has taken the best steps to calculate the spread of “subversive ideas” that may lead to terrorism so they can spot homegrown terrorists early before they strike. They have done a good job so far and have prevented several attacks already, including attempted bombings in Herald Square and JFK.

While civil libertarians may fret, this is actually a very old counterintelligence technique. It was used effectively to stamp down the Ku Klux Klan, the Nazi movement of the 1930s, anarchists and various militant and terrorist organizations.

This is an intelligence operation, but interestingly, they mostly use public source information. They do not spy on American citizens (and certainly not without a warrant) nor does a mere connection with a subversive idea mean a person will be arrested or harrassed by the police. They simply crunch the data like marketing analysts. They can then estimate the probability that a man is a true believer and the probability that he will commit a crime. If there is a sufficient threat, then they get a warrant and proceed like any other law enforcement investigation.

What’s new is the community network model which gives the technique more mathematical precision and will spare innocent civilians to a greater degree than previous operations.