It's four years since the terrible day in September 2001 when terrorists attacked New York City and killed nearly 3,000.  But the bombings on London trains and buses this summer were a reminder that New York is still vulnerable -- and they've led to controversy about the best way to stop terrorism without sacrificing American liberties.

New York has recovered from the attacks four years ago, and the economy and real estate are booming. Along Atlantic Avenue in Brooklyn, Muslim immigrants said the city feels safe, and they aren't worried about discrimination.

At Washington Square Park in Manhattan, where people rallied recently to save a famous rock music club, terrorism was far from most people's minds. But in Battery Park City, a block from Ground Zero, office workers taking a break on a late summer day said the memory of 9/11 hasn't faded. 

"I think the city's recovered to a new normal,? said Morris Friedman, an accountant. ?I don't think anything's ever going to be the way it was before. Something in our spirit is not as free and easy."

A financial analyst, who gave her first name as Rosalie, agreed: "You go on with your everyday life,? she said, ?but you're definitely a lot more cautious. Or you think back to what happened and every time you go under a tunnel or over a bridge, it passes people's minds, it goes through your mind at some point. I mean, it's a new day and you're going forward, but you just don't know."

After the London bombings, New York began random searches of bags of people entering some of its more than 460 subway stations.  Police set up checkpoint tables at different stations every few hours where people are stopped, without regard to external factors such as race, nationality, gender or age. Those who don't want their bags to be searched can simply go to another station a few blocks away, however. 

That's led civil libertarians to charge that the program violates the Constitutional prohibition against searches that aren't based on individual suspicion -- without meeting the test of actually improving public security.  They also raise concerns about the risk that people from the Middle East or South Asia will be singled out.

Donna Lieberman is the executive director of the New York Civil Liberties Union, which has filed a federal lawsuit against the program. "New Yorkers lived through September 11, we hurt on September 11, we were afraid on September 11 and thereafter,? she said in an interview. ?We suffered, and we don't want to go through that again. We want real security. We don't want a sham, feel-good solution, and another one of these needle in a haystack approaches to fighting terrorism."

"What are they talking about rejoins Dorothy Rabinowitz, an editorial writer at the Wall Street Journal,  ?[Are they saying that] The police, police excesses are a greater threat than terrorists who want to kill us?"  Ms. Rabinowitz blames oversensitivity to civil liberties for shielding the 9/11 terrorists, and says even a partial program of searching in the subways is better than none. 

"Every effort at surveillance has that one very potent effect,? she says, ?which is that it will make you think twice.? Ms. Rabinowitz also argues that police should be free to use ethnic and demographic "profiling," considering race, age, gender and other such factors in deciding whom to search. 

Referring to the September 11 lead hijacker she says, ?There were people at the airline counters who looked at Mohammed Atta, thought he was a terrorist, and were afraid to complain for fear that they would be accused of racial profiling."

Donna Lieberman responds that racial profiling is discriminatory because it singles people out regardless of their actions. She says that also damages society and doesn?t prevent terrorism. " It's both over-inclusive and under-inclusive,? she says. ?Remember Richard Reed, the shoe bomber? Gosh, he didn't even have an Arab name, so he wasn't a suspect.?

As for where ordinary New Yorkers stand on the security measures, those we spoke to mostly opposed racial profiling, but supported the bag searches ? or weren?t strongly opposed to them. "I think it's more of a deterrent kind of thing,? said a subway musician, adding, ?I think if you know there's a possibility you're going to be searched, it's less likely that you're going to try anything." 

Muslim immigrants from half a dozen nations in Brooklyn also supported the bag searches universally, saying they would increase public safety, and wouldn?t target Muslims unfairly.

An Iraqi-American man said, ?America is free, and I hope it will always be free, but they should have some rules not to let those people who are giving bad examples for the Muslims and Islam to get away with their crimes." 

But a young American-born man in Washington Square Park disagreed, saying the searches were not an effective way to prevent terrorism.  ?It?s the war [that makes us vulnerable],? he said, ?If we're going to keep going on with the war, there's a possibility that somebody's going to attack us. Searching everyone's makeup kit on the 1-9 train isn't the solution."

An Asian woman also supported the bag searches, but expressed suspicion that racial profiling is being used despite the policy prohibiting it.  "I have a boyfriend who's from an Islamic country, and he's been searched almost three times,? she said.  Several others pointed out that terrorists can come from any nation, and sometimes are American-born Caucasians. 

"Like most New Yorkers, I'm very sure there's going to be another attack here,? said a middle-aged woman. ?In some ways it feels helpful that there's some policy in place,? she went on, ?but I think if they search some person's backpack, or there's a threat of that, they'll just go to another train station, so I don't know if it will be effective.?

Whatever the courts decide, the subway searches may become less noticeable in time. The Metropolitan Transportation Authority recently announced an award of  $212 million to defense contractor Lockheed Martin to install high-tech surveillance systems throughout the New York transportation system, including more than 1,000 cameras, software to detect suspicious packages, and 3,000 motion sensors.