The nation's largest police department, with about 37,000 officers, has spent tens of millions of dollars - much it from federal grants - on an array of high-tech security measures designed to thwart threats potentially more daunting than another attack on a downtown skyscraper. It's also assigned 1,000 officers to counterterrorism duty, including 10 detectives posted around the globe who collect and share intelligence.
Overall, it's an effort unmatched by any other city in the nation, and perhaps the world.
"We've made major changes in this organization since Sept. 11," Police Commissioner Raymond Kelly said in a recent interview. "I think they're working. But it's still very much a work in progress."
David Cohen - a former CIA official brought aboard after Sept. 11 to head the NYPD's intelligence division - said the department has identified more than a dozen serious plots against the city in the past seven years that were either interrupted or abandoned, including some that haven't become public.
Among those that have come to light: a planned cyanide attack on the subways by al-Qaida operatives that authorities say was called off in 2002; another aborted al-Qaida plot to destroy the Brooklyn Bridge in 2003; a local scheme to blow up the subway station at Herald Square in 2004, resulting in the arrest and conviction of a Pakistani immigrant; and a plot to bomb underwater train tunnels to flood lower Manhattan, which was broken up in 2006 by several arrests overseas.
For terrorists, attacking New York City "is marbled into their thought process," Cohen said. "If you want to get into the major leagues in the terrorism business, you come here."
Cohen and Richard Falkenrath, the department's counterterrorism chief, drive home that point in daily briefings with Kelly.
On one recent morning in the commissioner's 14th floor conference room, the pair told him that in the past 24 hours, a Pakistani-born U.S. citizen had come forward to warn that his roommates in the Bronx wanted to attack the subway, that there had been multiple bomb threats against the U.S. Open tennis tournament and that an anonymous caller in Italy had told the CIA, "I put a bomb in New York."
Falkenrath said the Bronx case, like the others, was a false alarm: Investigators believe it may have stemmed from a dispute over money.
"It doesn't look like it's going to turn into a terrorism case," Falkenrath, a security expert who served in the White House until joining the NYPD, told Kelly.
Cohen also informed the commissioner that two NYPD detectives sent to Kosovo and Montenegro to gauge the threat of Islamic extremism in the Balkan region would be coming back with "a lot of valuable information."
The briefings are derived in part from classified information shared by federal law enforcement. But there also are reports from the NYPD's own team of analysts who have studied the rise of homegrown terror cells, and dispatches from investigators posted in Madrid, London, Paris, Tel Aviv, Singapore, Montreal, Toronto, Lyon, France, Santo Domingo, Dominican Republic, and Amman, Jordan.
Alerts also come from a separate team of investigators, most foreign-born and fluent in languages like Arabic and Farsi, who comb jihadist Web sites for signs of trouble.
The post-Sept. 11 endeavors so far haven't unearthed any "immediate threats against ground zero," Kelly said. "But we are very much concerned about that location as projects there go forward."
The NYPD is so concerned that it's spending $90 million to secure the trade center site, Wall Street and other parts of lower Manhattan using a series of checkpoints and 3,000 closed-circuit cameras monitored by officers at a command center. It was modeled in part after the "ring of steel" surveillance measures in London's financial district.
Also in the works is a project to use license-plate readers, radiation detectors and cameras installed at 16 bridges and four tunnels to screen every car, truck or other vehicle entering Manhattan for radioactive materials and other terrorism threats.
About a million vehicles drive onto the island everyday.
The vehicle data - license plate numbers, radiological readings and photos - would be automatically analyzed by computers programmed with information about suspicious vehicles. Police say the system could help them intercept would-be attackers before they can do harm.
The department has coordinated with police forces in New Jersey, Long Island and towns north of the city to expand the line of defense against terrorists transporting a dirty bomb or - most frightening of all - a nuclear device.
"If we're so unfortunate that terrorists actually acquire these weapons, this is by far the most likely place they'll seek to use them," Falkenrath said.
With the city certain to remain a prime target for terror, the police department can't let down its guard, Kelly said.
"We can put in a lot of measures, a lot of procedures and brag about what we're doing," he said. "But preventing another attack - that's the ultimate standard. So far, so good."
