Local Networks as Counterterrorism Tools

I don't have much to add to this story from In Homeland Security, except to say I think it's spot-on:

Israel places a high value on Human Intelligence and weaves HUMINT into all aspects of their law enforcement activities. A prevalent saying in their intelligence community guides their efforts: “the small bring in the big”. Israeli law enforcement and intelligence collection agents build long term, lasting relationships on the ground with all types of business people.

For instance waitresses, bartenders, taxi drivers and barbers can be a wealth of information. Emergency room employees, gas station workers, and grocery or drug store employees are all good collection sources. Around a specific target, street vendors are worthy of engagement since they frequent the same area and have a perfect viewpoint for noticing out-of-the-ordinary activity. If protecting a church is the objective, the clergy and worshippers are valuable informants.

The key is to cultivate the relationship; visit the sources regularly, build their trust, instruct them on what to look for, and make sure they have a way of contacting you 24/7 if they notice something suspicious. Your sources are force multipliers and critical to gleaning the information needed to identify, monitor and then disrupt terrorist activities. ...

If illegal weapons such as grenades are needed, the builder will need to move out of the circle of those aware of the plot, potentially exposing him and the planners. Well cultivated sources will notice this unusual activity and alert you.

Any kind of malicious actor is vulnerable to exposure at certain stages, because they have certain material needs that must be filled. Building a local network, cultivating relationships and - importantly - instructing your partners on what to look out for - is indeed a "force multiplier" in detecting these moments of exposure.