These are, admittedly, not the sort of assignments that investigators envision when they join the New York Police Department. But such missions, however mundane, have become as much a part of police counterterrorism efforts as the posting of detectives in places like Tel Aviv and Singapore, the planning for a bioterror attack or the identification of Arab speakers on the force.

Involving more grunt work than glamour, the city's counterterrorism effort has largely been built atop a nuts-and-bolts program of cultivating contacts with the businesses that might become unwitting parts of the next terror plot. Detectives visit scuba shops and hardware stores. They talk to parking garage attendants and plastic surgeons, hotel managers and tool rental companies, bulk fuel dealers and trade schools.

Called Operation Nexus, the program has focused on particular types of businesses based on intelligence that the department has culled from sources like an Al Qaeda manual for terrorist operatives and debriefings of some of the group's leaders and foot soldiers, said David Cohen, the deputy commissioner for intelligence.

Those debriefings and other evidence have suggested, among other things, that Al Qaeda has at least considered, if not plotted, using scuba divers to blow up bridges, riding in tourist helicopters for surveillance, turning trucks and limousines into rolling bombs and using special torches to cut the cables of the Brooklyn Bridge.

And Mr. Cohen noted that Qaeda members are trained to avoid the police.

"The next Mohamed Atta is far more likely to intersect with someone in the private sector than a law enforcement officer," he said, referring to the leader of the Sept. 11 plot.

Mr. Cohen, a former deputy director of the Central Intelligence Agency, who oversees the program, said it is based on personal contact with people and repeated visits to various businesses. "If you take the time to talk to people, it leaves an imprint," he said.

The effort is focused largely in and around New York City, where six or so detectives have made close to 20,000 visits, returning to some businesses time and again to leave their business cards and the department's terrorism hot line number. The detectives are encouraged to spend time with the businesses, leaving an outline of what they describe as possibly suspicious activity tailored for each type of business: more than 60 altogether, said Lt. Christopher S. Higgins, whom police officials credit with developing the program from concept to reality.

At an agricultural or mosquito-spraying business, which the authorities fear could be used to spread a biological agent like anthrax, the detectives cite possible warning signs like the loss, theft or attempted theft of equipment or machine components. They tell business owners to call if they encounter evasive customers who inquire about equipment but seem to lack previous experience in the industry.

Businesses that offer used emergency vehicles for sale are told to watch for requests to buy fire or police vehicles with radios or other equipment intact. Army-Navy and uniform stores are warned to watch for people who say they are in the military or civil service but who make statements suggesting their stories are false.

"We're going to have eyeball-to-eyeball contact with that individual who may be approached by someone who wants to do harm to our city," Mr. Cohen said, noting that the business owners themselves can best spot an anomaly.

Police Commissioner Raymond W. Kelly, who instituted the program, said it quickly expanded from its initial focus on explosives and marinas, at a time when there was heightened concern about terrorists using boats in attacks, to a wide range of other businesses. They include chemical and insecticide companies, livery car businesses, truck and van rentals, travel agencies and self-storage businesses, where the authorities fear terrorists could store explosives or radioactive materials for a dirty bomb.

"We're looking for anything that with a little thought could be used by a terrorist," Mr. Kelly said.

[...]

Other jurisdictions, including the Metropolitan Police in London, have studied New York's program and are trying to use it as a model in some fashion, Lieutenant Higgins said. The New York State Office of Public Security recently put in place a mirror image of the city's program across the state.

[...]

Lieutenant Higgins said he usually fields three teams of two detectives each day, and they are expected to visit more than a dozen sites a day. Each visit is recorded in an extensive database that tracks the contacts, listing the detective assigned, the type of business, hours of operation, those who were spoken to, and whether they have any security equipment, like video cameras, that can capture images of people who come in.

It's a good idea; it's a force-multiplier in a big way, enlisting the front line of defense: the citizenry. I'd throw at least a few dozen more cops at it, if not a couple of hundred (given that NYC has approximately 20,000 police officers, not counting civilian employees, I think they can be spared). And, yes, more jurisdictions should adopt this program insofar as it's an effective use of police staff levels.

Read The Rest Scale: 2.5 out of 5.

Gary Farber's home blog is Amygdala.