In the last several weeks, as preparations for the war against Iraq have heated up, it has begun to sink in that this will be a different conflict from what we have seen before -- that there may, in fact, be two fronts, one far away on the ground in the Middle East, the other right here at home. For the first time in history, it seems plausible that an enemy might mount a sustained attack on the United States, using weapons of terrorism. The term ''soft targets,'' which refers to everyday places like offices, shopping malls, restaurants and hotels, is now casually dropped into conversation, the way military planners talk about ''collateral demage.''

Earlier this month, the federal government raised the official terrorism alert level and advised Americans to prepare a ''disaster supply kit,'' including duct tape to seal windows against airborne toxins. Members of Congress organized news conferences to demand that passenger jets be outfitted with missile-avoidance systems. In major public areas of cities, the police presence has been especially conspicuous, with weapons ostentatiously displayed. Whatever the details, the message was the same: war is on the way here.

The impossible questions begin with where, what and how, and end with what to do about it. Sgt. George McClaskey, a Baltimore cop, spends his days thinking about the answers, and one cold day recently, he took me out in an old police launch to survey Baltimore harbor. He showed me some of the new security measures, like the barriers at the approach to the harbor, which rose out of the water like stakes in a moat. Cables were suspended between these reinforced pylons, designed to slice into approaching high-speed craft and decapitate would-be suicide bombers before they reached their mark. It looked fairly daunting.

Jason Fulford, Illustration by Nicholas Blechman

Then McClaskey maneuvered the boat toward an unprotected stretch of Baltimore's Inner Harbor. With the temperature dipping into the teens, the place was empty. But when the weather is warm, up to a quarter of a million people congregate on these piers and brightly painted promenades every weekend.

''If I wanted to create a big bang,'' McClaskey said, adopting the mind-set of a suicide bomber, ''I'd pack a small boat with explosives and crash it right there.'' He pointed to a promenade. ''It'd be a catastrophe,'' he declared. ''It would take 48 hours just for the tide to flush out the bodies from under the boardwalk.''

The port is lined with large oil terminals, storage tanks and petrochemical facilities, incendiaries in need only of a lighted fuse. Even the Domino sugar refinery, with its sticky-sweet flammable dust, poses a threat. ''Most people don't think about it,'' McClaskey said, ''but that's a giant bomb.''

The list of vulnerabilities is perilously long in Baltimore, as it is just about everywhere in the United States. And every one of those potential targets can set in motion an ever-broadening ripple effect. Should terrorists manage to blow up an oil terminal in Baltimore, for instance, the nearby ventilation systems for the I-95 tunnel would have to be shut. Shut down the tunnel, and the Interstate highway must be closed. Close down a section of I-95, and traffic along the entire Eastern Seaboard snarls to a halt.

''So how would you defend against frogmen blowing up half the harbor?'' I asked McClaskey.

The sergeant shrugged uneasily. ''Honestly,'' he confessed, ''I don't think it's possible.'' Like most law enforcement officers in this country, McClaskey has been trained to catch crooks, not to stop submerged suicide bombers. Imagining doomsday possibilities is one thing; we've all become good at it these past 18 months. Coming up with counterterror solutions is another story, often beyond the scope of our imaginations. But while that expertise may not yet exist in the United States, it's out there, if you know where to look.

''Sonar,'' replied Rear Adm. Amiram Rafael, when I put the same question to him 6,000 miles away in Israel, perhaps the one place in the world where terrorism is as much a part of daily life as commuter traffic. ''It can distinguish between humans and large fish by mapping movement patterns and speed.'' Rafael spent 28 years protecting Israel's coastline from terrorists and now consults for foreign clients. ''If the alarm sounds, rapid response units in fast boats are dispatched,'' he said. ''They're equipped with underwater concussion grenades.''

''To stun the divers?'' I asked.

''No,'' Rafael said, flashing a fatherly smile. ''To kill them.''

Until recently, the United States and countries like Israel occupied opposite ends of the security spectrum: one a confident and carefree superpower, seemingly untouchable, the other a tiny garrison state, surrounded by fortifications and barbed wire, fighting for its survival. But the security gap between the U.S. and places like Israel is narrowing. Subways, sewers, shopping centers, food processing and water systems are all now seen as easy prey for terrorists. 

There is no clear consensus yet on how to go about protecting ourselves. The federal government recently concluded a 16-month risk assessment, and last month, the new Department of Homeland Security was officially born, with an annual budget of $36 billion. Big money has already been allocated to shore up certain perceived weaknesses, including the $5.8 billion spent hiring, training and equipping federal airport screeners and the $3 billion allocated for ''bioterrorism preparedness.'' All that has been well publicized. Other measures, like sophisticated radiation sensors and surveillance systems, have been installed in some cities with less fanfare. Meanwhile, the F.B.I. is carrying out labor-intensive tasks that would have seemed a ludicrous waste of time 18 months ago, like assembling dossiers on people who take scuba-diving courses.

This marks only the very beginning. A national conversation is starting about what kind of country we want to live in and what balance we will tolerate between public safety and private freedom. The decisions won't come all at once, and we may be changing our minds a lot, depending on whether there are more attacks here, what our government tells us and what we believe. Two weeks ago, Congress decided to sharply curtail the activities of the Total Information Awareness program, a Pentagon project led by Rear Adm. John Poindexter and invested with power to electronically sift through the private affairs of American citizens. For the time being, it was felt that the threat of having the government look over our credit-card statements and medical records was more dangerous than its promised benefits.

Congress didn't completely shut the door on the T.I.A., though. Agents can still look into the lives of foreigners, and its functions could be expanded at any time. We could, for instance, reach the point where we demand the installation of systems, like the one along the Israeli coastline, to maim or kill intruders in certain sensitive areas before they have a chance to explain who they are or why they're there. We may come to think nothing of American citizens who act suspiciously being held without bail or denied legal representation for indeterminate periods or tried in courts whose proceedings are under seal. At shopping malls and restaurants, we may prefer to encounter heavily armed guards and be subjected to routine searches at the door. We may be willing to give up the freedom and ease of movement that has defined American life, if we come to believe our safety depends upon it. For the better part of a generation now, Americans have gone to great lengths to protect their homes -- living in gated communities, wiring their property with sophisticated alarms, arming themselves with deadly weapons. Now imagine this kind of intensity turned outward, into the public realm. As a culture, our tolerance for fear is low, and our capacity to do something about it is unrivaled. We could have the highest degree of public safety the world has ever seen. But what would that country look like, and what will it be like to live in it? Perhaps something like this.

Electronic Frisking Every Day on Your Commute

As a homebound commuter entering Washington's Foggy Bottom subway station swipes his fare card through the turnstile reader, a computer in the bowels of the mass transit authority takes note. A suspicious pattern of movements has triggered the computer's curiosity.

The giveaway is a microchip in the new digital fare cards, derived from the electronic ID cards many of us already use to enter our workplaces. It could be in use throughout the U.S. within a couple of years. If embedded with the user's driver's license or national ID number, it would allow transportation authorities to keep tabs on who rides the subway, and on when and where they get on and off.

The commuter steps through the turnstile and is scanned by the radiation portal. These would be a natural extension of the hand-held detectors that the police have started using in the New York subways. A cancer patient was actually strip-searched in a New York subway station in 2002 after residue from radiation treatments tripped the meters. But this doesn't happen to our fictitious commuter. The meters barely flicker, registering less than one on a scale of one to nine, the equivalent of a few microroentgens an hour, nowhere near the 3,800 readout that triggers evacuation sirens.

Imagine a battery of video cameras following the commuter's progress to the platform, where he reads a newspaper, standing next to an old utility room that contains gas masks. Cops in New York already have them as part of their standard-issue gear, and a fully secure subway system would need them for everybody, just as every ferryboat must have a life preserver for every passenger. Sensors, which are already used in parts of the New York subway system, would test the air around him for the presence of chemical agents like sarin and mustard gases.

The commuter finishes reading his newspaper, but there is no place to throw it away because all trash cans have been removed, as they were in London when the I.R.A. used them to plant bombs. Cameras show the commuter boarding one of the subway cars, which have been reconfigured to drop oxygen masks from the ceiling in the event of a chemical attack, much like jetliners during decompression. The added security measures have probably pushed fares up throughout the country, maybe as much as 40 percent in some places.

The commuter -- now the surveillance subject -- gets off at the next stop. As he rides the escalator up, a camera positioned overhead zooms in for a close-up of him. This image, which will be used to confirm his identity, travels through fiber-optic cables to the Joint Operations Command Center at police headquarters. There, a computer scans his facial features, breaks them down into three-dimensional plots and compares them with a databank of criminal mug shots, people on watch lists and anyone who has ever posed for a government-issue ID. The facial-recognition program was originally developed at M.I.T. Used before 9/11 mainly by casinos to ferret out known cardsharps, the system has been tried by airport and law enforcement authorities and costs $75,000 to $100,000 per tower, as the camera stations are called.

''It can be used at A.T.M.'s, car-rental agencies, D.M.V. offices, border crossings,'' says an executive of Viisage Technology, maker of the Face-Finder recognition system. ''These are the sorts of facilities the 19 hijackers used.''

Almost instantly, the software verifies the subject's identity and forwards the information to federal authorities. What they do with it depends on the powers of the Total Information Awareness program or whatever its successors will be known as. But let's say that Congress has granted the government authority to note certain suspicious patterns, like when someone buys an airline ticket with cash and leaves the return date open. And let's say the commuter did just that -- his credit cards were maxed out, so he had no choice. And he didn't fill in a return date because he wasn't sure when his next consulting assignment was going to start, and he thought he might be able to extend his vacation a few days.

On top of that, let's say he was also indiscreet in an e-mail message, making a crude joke to a client about a recent airline crash. Software programs that scan for suspect words are not new. Corporations have long used them to automatically block employee e-mail containing, for instance, multiple references to sex. The National Security Agency's global spy satellites and supercomputers have for years taken the search capability to the next level, processing the content of up to two million calls and e-mail messages per hour around the world.

Turning the snooping technology on Americans would not be difficult, if political circumstances made it seem necessary. Right now, there would be fierce resistance to this, but the debate could swing radically to the other side if the government showed that intercepting e-mail could deter terrorists from communicating with one another. Already, says Barry Steinhardt, director of the A.C.L.U. program on technology and liberty, authorities have been demanding records from Internet providers and public libraries about what books people are taking out and what Web sites they're looking at.

Once the commuter is on the government's radar screen, it would be hard for him to get off -- as anyone who has ever found themselves on a mailing or telemarketers' list can attest. It will be like when you refinance a mortgage -- suddenly every financial institution in America sends you a preapproved platinum card. Once a computer detects a pattern, hidden or overt, your identity in the digital world is fixed.

Technicians manning the Command Center probably wouldn't know why the subject is on a surveillance list, or whether he should even be on it in the first place. That would be classified, as most aspects of the government's counterterrorist calculations are.

Nonetheless, they begin to monitor his movements. Cameras on K Street pick him up as he exits the subway station and hails a waiting taxi. The cab's license plate number, as a matter of routine procedure, is run through another software program -- first used in Peru in the 1990's to detect vehicles that have been stolen or registered to terrorist sympathizers, and most recently introduced in central London to nab motorists who have not paid peak-hour traffic tariffs. Technicians get another positive reading; the cabdriver is also on a watch list. He is a Pakistani immigrant and has traveled back and forth to Karachi twice in the last six months, once when his father died, the other to attend his brother's wedding. These trips seem harmless, but the trackers are trained not to make these sorts of distinctions.

So what they see is the possible beginning of a terrorist conspiracy -- one slightly suspicious character has just crossed paths with another slightly suspicious character, and that makes them seriously suspicious. At this moment, the case is forwarded to the new National Counterintelligence Service, which will pay very close attention to whatever both men do next.

The N.C.S. does not exist yet, but its creation is advocated by the likes of Lt. Gen. William Odom, a former head of the National Security Agency. Whether modeled after Britain's MI5, a domestic spy agency, or Israel's much more proactive and unrestricted Shin Bet, the N.C.S. would most likely require a budget similar to the F.B.I.'s $4.2 billion and nearly as much personnel as the bureau's 11,400-strong special agent force, mostly for surveillance duties.

N.C.S. surveillance agents dispatched to tail the two subjects in the taxi would have little difficulty following their quarry through Georgetown, up Wisconsin Avenue and into Woodley Park. One tool at their disposal could be a nationwide vehicle tracking system, adapted from the technology used by Singapore's Land Transport Authority to regulate traffic and parking. The system works on the same principle as the E-ZPass toll-road technology, in which scanners at tollbooths read signals from transponders installed on the windshields of passing vehicles to pay tolls automatically. In a future application, electronic readers installed throughout major American metropolitan centers could pinpoint the location of just about any vehicle equipped with mandatory transponders. (American motorists would most likely each have to pay an extra $90 fee, similar to what Singapore charges.)

When the commuter arrives home, N.C.S. agents arrange to put his house under 24-hour aerial surveillance. The same thing happens to the cabdriver when he arrives home. The technology, discreet and effective, is already deployed in Washington. Modified UH-60A Blackhawk helicopters, the kind U.S. Customs uses to intercept drug runners, now patrol the skies over the capital to enforce no-fly zones. The Pentagon deployed its ultrasophisticated RC-7 reconnaissance planes during the sniper siege last fall. The surveillance craft, which have proved their worth along the DMZ in North Korea and against cocaine barons in Colombia, come loaded with long-range night-vision and infrared sensors that permit operators to detect move-ment and snap photos of virtually anyone's backyard from as far as 20 miles away.

In the here and now, an aerial photo of my backyard is on file at the Joint Operations Command Center in Washington, which, unlike the N.C.S., already exists. The center looks like NASA, starting with the biometric palm-print scanners on its reinforced doors.

The center has not singled me out for any special surveillance. My neighbors' houses are all pictured, too, as are still shots and even three-dimensional images of just about every building, landmark and lot in central D.C.

The technology isn't revolutionary. How many times a day is the average American already on camera? There's one in the corner deli where I get my morning coffee and bagel. Another one at the A.T.M. outside. Yet another one films traffic on Connecticut Avenue when I drive my wife to work. The lobby of her office building has several. So that's at least four, and it's only 9 a.m.

There are few legal restraints governing video surveillance. It is perfectly legal for the government to track anyone, anywhere, using cameras except for inside his own home, where a warrant is needed to use thermal imaging that can see all the way into the basement. Backyards or rooftops, however, are fair game.

There is a growing network of video cameras positioned throughout the capital that feed into the Joint Operations Command Center, otherwise known as the JOCC, which has been operational since 9/11. The experimental facility is shared by several government agencies, including the Metropolitan Police Department, the F.B.I., the Secret Service, the State Department and the Defense Intelligence Agency. Agents from different law enforcement bodies man the JOCC's 36 computer terminals, which are arrayed in long rows beneath wall-size projection screens, like the Houston space center. The wall screens simultaneously display live feeds, digital simulations, city maps with the locations of recently released felons and gory crime scene footage.

From here we can tap into schools, subways, landmarks and main streets,'' says Chief Charles Ramsey of the D.C. Police, with evident pride. Theoretically, with a few clicks of the mouse the system could also link up with thousands of closed-circuit cameras in shopping malls, department stores and office buildings, and is programmed to handle live feeds from up to six helicopters simultaneously. Ramsey is careful to add that, for now, the majority of the cameras are off-line most of the time, and that the police aren't using them to look into elevators or to spy on individuals.

But they could if they wanted to. I ask for a demonstration of the system's capabilities. A technician punches in a few keystrokes. An aerial photo of the city shot earlier from a surveillance plane flashes on one of the big screens. ''Can you zoom in on Dupont Circle?'' I ask. The screen flickers, and the thoroughfare's round fountain comes into view. ''Go up Connecticut Avenue.'' The outline of the Hilton Hotel where President Reagan was shot materializes. ''Up a few more blocks, and toward Rock Creek Park,'' I instruct. ''There, can you get any closer?'' The image blurs and focuses, and I can suddenly see the air-conditioning unit on my roof, my garden furniture and the cypress hedge I recently planted in my yard.

The fact that government officials can, from a remote location, snoop into the backyards of most Washingtonians opens up a whole new level of information they can find out about us almost effortlessly. They could keep track of when you come and go from your house, discovering in the process that you work a second job or that you are carrying on an extramarital affair. Under normal circumstances, there's not much they could do with this information. And for the time being, that is the way most Americans want it. But this is the kind of issue that will come up over the next few years. How many extra tools will we be willing to grant to the police and federal authorities? How much will we allow our notions of privacy to narrow?

Because if domestic intelligence agents were able to find out secret details of people's lives, they could get the cooperation of crucial witnesses who might otherwise be inclined to keep quiet. There is more than a whiff of McCarthyism to all this, but perhaps we will be afraid enough to endure it.

The JOCC is also studying the effect of large-scale bombs in Washington. A three-dimensional map of all downtown buildings allows technicians to simulate bomb blasts and debris projections. They can also tap into the weather bureau for real-time data on wind speeds and directions to determine which parts of the city would have to be evacuated first in the event of a radiological or biochemical plume. Programmers are now working on an underground map of the capital that would show water and gas distribution and power grids.

Efforts are under way to establish facilities similar to the JOCC in big urban centers like Los Angeles, Chicago, Atlanta and New York. One benefit of the JOCC's is that they are relatively cheap to set up, particularly since most major cities already have surveillance equipment positioned in places like tunnels and bridges. Each command center would likely cost around $7 million to build, with an additional $15,000 charge for every camera installed.

There is also talk of connecting all the facilities together so that officials in different parts of the country could coordinate response efforts to terrorism. ''Attacks will likely occur in different cities simultaneously,'' Chief Ramsey says. And as for those civil libertarians uneasy with the notion of blanket national surveillance, Ramsey just shrugs. ''We can't pretend we live in the 19th century. We have to take advantage of technology.''

Imagine a wintry scene: snowdrifts and dirty slush and a long line of people muffled against the cold. This is a line to get into the mall, and it is moving frustratingly slowly. What's the holdup?

There is no new blockbuster movie opening that day, or any of those ''everything must go'' clearance sales that might justify standing outside freezing for 20 minutes. Customers are simply waiting to clear security.

Shopping in an environment of total terrorist preparedness promises to be a vastly different experience from anything ever imagined in America. But for millions of people who live in terror-prone places like Israel or the Philippines, tight security at shopping malls has long been a fact of life. ''I was shocked when I first came to the States and could go into any shopping plaza without going through security,'' says Aviv Tene, a 33-year-old Haifa attorney. ''It seemed so strange, and risky.''

It took me just under eight minutes to clear the security checkpoint outside the Dizengoff Center in downtown Tel Aviv. But that was on a rainy weekday morning before the food courts and multiplex theater had opened.

The future shopping experience will start at the parking-lot entrance. Booths manned by guards will control access to and from lots to prevent terrorists from emulating the Washington sniper and using parking lots as shooting galleries. Cars entering underground garages will have their trunks searched for explosives, as is the practice in Manila. It has also become common outside New York City hotels. This will guard against car or truck bombs of the type that blew up beneath the World Trade Center in 1993.

No one will be able to drive closer than a hundred yards to mall entrances. Concrete Jersey barriers will stop anyone from crashing a vehicle into the buildings -- a favored terrorist tactic for American targets overseas -- or into the crowds of customers lining up. Screening will follow the Israeli model: metal barricades will funnel shoppers through checkpoints at all doors. They will be frisked, and both they and their bags will be searched and run through metal detectors. Security would be tightest in winter, says a former senior F.B.I. agent, because AK-47's and grenade belts are easily concealed beneath heavy coats.

What won't be concealed, of course, are the weapons carried by the police at the mall. Major shopping areas will not be patrolled by the docile, paid-by-the-hour guards to whom we're accustomed, but -- like airports and New York City tourist attractions -- by uniformed cops and soldiers with rifles.

What will it be like to encounter such firearms on a regular basis? I lived for years in Moscow, and after a short time, I rarely noticed the guns. In fact, I tended to feel more uncomfortable when armed guards were not around; Israelis traveling in the United States occasionally say the same thing. But despite the powerful presence of guns in popular culture, few Americans have had much contact with the kind of heavy weapons that are now becoming a common sight on city streets. Such prominent displays are meant to convey the notion that the government is doing something to ward off terrorists, but they can have the reverse effect too, of constantly reminding us of imminent danger.

Even more mundane procedures might have the same effect -- for example, being asked to produce a national identification card every time you go into a store, much the same way clubgoers have to prove they are of age. The idea of a national identity card, once widely viewed as un-American, is gaining ground in Washington, where some are advocating standardizing driver's licenses throughout the country as a first step in that direction. Though perhaps reminiscent of Big Brother, these cards are not uncommon in the rest of the world, even in Western Europe. In Singapore, the police frequently ask people to produce their papers; it becomes so routine that people cease being bothered by it. How long would it take Americans to become similarly inured?

The new ID's, which are advocated by computer industry leaders like Larry Ellison of Oracle, could resemble the digital smart cards that Chinese authorities plan to introduce in Hong Kong by the end of the year. These contain computer chips with room to store biographical, financial and medical histories, and tamper-proof algorithms of the cardholder's thumbprint that can be verified by hand-held optical readers. Based on the $394 million Hong Kong has budgeted for smart cards for its 6.8 million residents, a similar program in the U.S. could run as high as $16 billion.

Among other things, a national identity card program would make it much harder for people without proper ID to move around and therefore much easier for police and domestic-intelligence agents to track them down. And once found, such people might discover they don't quite have the rights they thought they had. Even now, for instance, U.S. citizens can be declared ''enemy combatants'' and be detained without counsel. Within a few years, America's counterterrorist agencies could have the kind of sweeping powers of arrest and interrogation that have developed in places like Israel, the Philippines and even France, where the constant threat of terrorism enabled governments to do virtually whatever it takes to prevent terrorism. ''As long as you worry too much about making false arrests and don't start taking greater risks,'' says Offer Einav, a 15-year Shin Bet veteran who now runs a security consulting firm, ''you are never going to beat terrorism.'' 

In years past, the U.S. has had to rely on other governments to take these risks. For example, the mastermind of the 1993 W.T.C. bombing, Ramzi Yousef, was caught only after Philippine investigators used what official intelligence documents delicately refer to as ''tactical interrogation'' to elicit a confession from an accomplice arrested in Manila. In U.S. court testimony, the accomplice, Abdul Hakim Murad, later testified that he was beaten to within an inch of his life. Advertisement

In Israel, it is touted that 90 percent of suicide bombers are caught before they get near their targets, a record achieved partly because the Shin Bet can do almost anything it deems necessary to save lives. ''They do things we would not be comfortable with in this country,'' says former Assistant F.B.I. Director Steve Pomerantz, who, along with a growing number of U.S. officials, has traveled to Israel recently for antiterror training seminars.

But the U.S. is moving in the Israeli direction. The U.S.A. Patriot Act, rushed into law six weeks after 9/11, has given government agencies wide latitude to invoke the Foreign Intelligence Surveillance Act and get around judicial restraints on search, seizure and surveillance of American citizens. FISA, originally intended to hunt international spies, permits the authorities to wiretap virtually at will and break into people's homes to plant bugs or copy documents. Last year, surveillance requests by the federal government under FISA outnumbered for the first time in U.S. history all of those under domestic law.

New legislative proposals by the Justice Department now seek to take the Patriot Act's antiterror powers several steps further, including the right to strip terror suspects of their U.S. citizenship. Under the new bill -- titled the Domestic Security Enhancement Act of 2003 -- the government would not be required to disclose the identity of anyone detained in connection with a terror investigation, and the names of those arrested, be they Americans or foreign nationals, would be exempt from the Freedom of Information Act, according to the Center for Public Integrity, a rights group in Washington, which has obtained a draft of the bill. An American citizen suspected of being part of a terrorist conspiracy could be held by investigators without anyone being notified. He could simply disappear.

Some aspects of life would, in superficial ways, seem easier, depending on who you are and what sort of specialized ID you carry. Boarding an international flight, for example, might not require a passport for frequent fliers. At Schiphol Airport in Amsterdam, ''trusted'' travelers -- those who have submitted to background checks -- are issued a smart card encoded with the pattern of their iris. When they want to pass through security, a scanner checks their eyes and verifies their identities, and they are off. The whole process takes 20 seconds, according to Dutch officials. At Ben-Gurion in Israel, the same basic function is carried out by electronic palm readers.

''We start building dossiers the moment someone buys a ticket,'' says Einav, the Shin Bet veteran who also once served as head of El Al security. ''We have quite a bit of information on our frequent fliers. So we know they are not a security risk.''

The technology frees up security personnel to focus their efforts on everybody else, who, on my recent trip to Jerusalem, included me. As a holder of a Canadian passport (a favorite of forgers) that has visa stamps from a number of high-risk countries ending in ''stan,'' I was subjected to a 40-minute interrogation. My clothes and belongings were swabbed for explosives residue. Taken to a separate room, I was questioned about every detail of my stay in Israel, often twice to make certain my story stayed consistent. Whom did you meet? Where did you meet? What was the address? Do you have the business cards of the people you met? Can we see them? What did you discuss? Can we see your notes? Do you have any maps with you? Did you take any photographs while you were in Israel? Are you sure? Did you rent a car? Where did you drive to? Do you have a copy of your hotel bill? Why do you have a visa to Pakistan? Why do you live in Washington? Can we see your D.C. driver's license? Where did you live before Washington? Why did you live in Moscow? Are you always this nervous?

A Russian speaker was produced to verify that I spoke the language. By the time I was finally cleared, I almost missed my flight. ''Sorry for the delay,'' apologized the young security officer. ''Don't take it personally.''

El Al is a tiny airline that has a fleet of just 30 planes and flies to a small handful of destinations. It is also heavily subsidized by the government. This is what has made El Al and Ben-Gurion safe from terrorists for more than 30 years.

Getting the American airline system up to this level would require a great deal more than reinforced cockpit doors and the armed air marshals now aboard domestic and international flights. It would require changing everything, including the cost and frequency of flights. Nothing could be simpler, right now, than flying from New York to Pittsburgh -- every day, there are at least a dozen direct flights available from the city's three airports and countless more connecting flights. Bought a week or two in advance, these tickets can be as cheap as $150 round-trip. 

Making U.S. airlines as security-conscious as El Al would put the U.S. back where the rest of the world is -- maybe a flight or two a day from New York to Pittsburgh, at much higher costs, and no assurance whatsoever you can get on the plane you want. Flights would take longer, and landings might be a little more interesting, because pilots would have to stay away from densely populated areas, where a plane downed by a shoulder-launched Stinger missile could do terrible damage.

Kayaking in the Wrong Place Is a Federal Crime

In a state of full readiness, American cities would be a patchwork of places you couldn't go near. At first, most people wouldn't even notice when no-sail zones were instituted around all 50 major industrial ports in the country. Maybe they would find out when they went to a local marina where they occasionally rent a small outboard to go water-skiing and found that it had been closed and relocated. Or maybe they went kayaking up near the Indian Point nuclear plant on the Hudson and spent an afternoon talking to the Coast Guard after they got a little too close.

There may be a lot of places private boats will be unable to go, like anywhere near a shipping channel used by oil and gas freighters. Infrared and video optronic systems that can detect small boats, and even inflatable rubber craft, may be deployed to enforce the no-sail zones. ''We invented it after terrorists rode a freighter to within 10 miles of Tel Aviv,'' says Rafael, the former Israeli rear admiral, ''and used inflatable boats to attack beachfront hotels.''

Each optronic installation costs $2 million, and four or five of the units would be needed to protect the approach to any major harbor, Rafael says. The system would thus cost around $500 million.

''I'm always amazed at how lightly defended your industry is compared to most other countries,'' says Hezy Ribak, another Israeli intelligence expert, who runs a security consulting firm. ''In Israel, we treat security at our industrial facilities the way we do borders. The stakes,'' he adds, ''are just as high, higher if you consider the damage terrorists can do if they infiltrate a nuclear power plant or blow up a gas reservoir.''

The P-Glilot natural gas reservoir near Tel Aviv is a good example of what security experts like Ribak have in mind for the U.S. From a distance, P-Glilot doesn't seem all that different than similar installations in New Jersey, Ohio or Texas. The massive storage tanks are even painted with quaint butterflies and birds. But just off the highway, watchtowers dot the landscape. If you drive closer, the complex takes on the feel of a military garrison, with high walls and electric fences bristling with sensors and cameras, and notices posted in Hebrew, English and Arabic warning: ''No Photography.'' Pull off the road and park by the perimeter fence for a mere 15 seconds, and a metallic voice sounds from an unseen loudspeaker, calling out your license plate number and telling you to move on. ''Security,'' Einav says, ''is about layers, creating buffer zones.'' On the ground, that means changing the way industrial sites are guarded. Security precautions in the U.S. are concentrated around the core of the targets -- be they reactors, pumping stations or chemical plants -- rather than the perimeter.

''Security at the main buildings might stop environmental protesters or the lone crazy, but it doesn't help in the case of a truck loaded with explosives, because the terrorists have already reached their objective,'' Ribak says. ''Why give yourself so little room? There should be as big a buffer as possible between the first line of defense -- the perimeter of the property -- and the target, to give yourself early warning.''

Perimeters, Ribak says, will need to be equipped with vibration sensors; thermal and infrared cameras; buried magnetic detection devices that can distinguish between humans, animals and vehicles; and several rows of old-fashioned razor coil to delay intruders, giving guards time to respond to alarms.

In the U.S., where many industrial facilities are concentrated in dense urban areas, such security measures would necessitate the rerouting of highways and possibly the relocation of neighborhoods that are just too close. In New York City, power plants sit right in the middle of residential neighborhoods, like the one at 14th Street and Avenue D in the East Village. It is across the street from Stuyvesant Town and a public housing project, home to tens of thousands of people. Israeli security officials shake their heads in astonishment at such ''crazy'' U.S. practices, but then again who ever thought that putting an airport next to the Pentagon was a security risk? 

Securing dense, mixed-use urban neighborhoods could not only complicate housing markets and commuting patterns, which are typically a disaster in most cities already, but could also come at tremendous expense. Consider the Donald C. Cook nuclear power plant in Berrien County, Mich. It has two Westinghouse reactors and sits on a relatively cramped 650-acre plot. Just to provide a three-mile buffer around the plant would run $76 million, according to U.S.D.A. statistics on the average price per acre of land in Michigan. For the Indian Point plant in Westchester, the cost would be exponentially higher. Add to that the $3.5 billion to $7 billion estimated by a recent Princeton University study to safeguard spent fuel pools from air attack, the roughly $3.5 million price tag of new perimeter sensors and the $160 million that Raytheon charges for a Patriot missile battery capable of knocking out airborne threats, and multiply the total by the 103 nuclear power stations in the country.

Now factor in the 276,000 natural gas wells in the U.S., the 1.5 million miles of unprotected pipelines, the 161 oil refineries, 2,000 oil storage facilities and 10,400 hydro, coal and gas-fired power generating stations, and you get a sense of the costs involved.

But you probably won't be thinking about any of that when you go out to dinner or to the movies or to a ball game. By then, it could all be second nature. The restaurant attendant will go through your purse and wave a metal-detector wand over your jacket, as they do in Tel Aviv. The valet parker will pop open your trunk and look through it before dropping your car off at an underground garage, just as in Manila.

If you take the family to a Dodgers game, you'll be able to tell your kids how, back in the day, they used to have blimps and small planes trailing ad banners over stadiums. The flight restrictions, started at Super Bowl XXXVII in 2002, would not permit any planes within seven miles of any significant sporting events. Fans would have to park at least five miles from the stadium and board shuttle buses to gates. Spectators would be funneled through airport-style metal detectors and watched over by a network of 50 cameras installed throughout the stadium. Air quality would be monitored for pathogens by the type of portable detectors brought in by the Army at last year's Olympics.

Even people with no interest in sports who live in high-rises near stadiums would know whenever game day came round. ''Tall buildings near stadiums are also a risk,'' says Col. Mena Bacharach, a former Israeli secret-service agent who is one of the lead security consultants for the 2004 Summer Olympics in Athens. ''They would have to be swept for snipers or R.P.G.'s.'' R.P.G.'s? Those are rocket-propelled grenades, another term that could become an American colloquialism.

It's still too early to tell what all this would mean to ticket prices, but, in a sign of the changing times, the security allocation alone for last month's Super Bowl was $9 million -- the equivalent of $134 for every one of the 67,000 fans in attendance.

Of course, public awareness programs could help to significantly cut down counterterror costs. In Israel, televised public service announcements similar to antidrug commercials in the U.S. warn viewers to be on the lookout for signs of suspicious activity. The messages are even taught to schoolchildren, along with other important survival tips, like how to assemble gas masks. ''I was out with my 7-year-old granddaughter the other day,'' recalls Joel Feldschuh, a former Israeli brigadier general and president of El Al. ''And she sees a bag on the street and starts shouting: 'Granddaddy, granddaddy, look. Quickly call a policeman. It could be left by terrorists.' ''

It is commonly held that a country as big and confident in its freedoms as the United States could never fully protect itself against terrorists. The means available to them are too vast, the potentially deadly targets too plentiful. And there is a strong conviction in many quarters that there is a limit to which Americans will let their daily patterns be disturbed for security precautions. Discussing the possibility that we might all need to be equipped with our own gas masks, as Israelis are, Sergeant McClaskey of Baltimore assured me it would never happen. ''If it ever reaches the point where we all need gas masks,'' McClaskey said, shaking his head with disgust, ''then we have lost the war on terror because we are living in fear.''

What does it really mean, however, to ''lose the war on terror''? It's as ephemeral a concept as ''winning the war on terror.'' In what sense will it ever be possible to declare an end of any kind?

One thing that makes the decisions of how to protect ourselves so difficult is that the terrorism we face is fundamentally different from what other governments have faced in the past. The Israelis live in tight quarters with an enemy they know well and can readily lay their eyes on. Terror attacks on European countries have always come from colonies or nearby provinces that have generally had specific grievances and demands. Americans don't know exactly who our enemies are or where they are coming from. Two of the recent thwarted terrorists, Richard Reid and Zacarias Moussaoui, were in fact Europeans.

The United States also lacks the national identity that binds Israel and most European countries and helps make the psychic wounds of terrorism heal faster. In Israel, hours after a bombing, the streets are crowded again -- people are determined to keep going. Immediately after 9/11, that's how many Americans felt, too, but it's not at all clear how long this kind of spirit will endure.

Nor is it clear how we will absorb the cost. An adviser to President Bush estimates that as much as $100 billion will have to be spent annually on domestic security over the next 10 years, if you factor in all the overtime accrued by police departments every time there is a heightened alert. There are many who believe, as General Odom does, that the money is ''insignificant.'' ''At the height of the cold war we used to spend 7.2 percent of G.D.P. on defense and intelligence,'' he says. ''We spend less than half that now.''

Outside of defense and some of the entitlement programs, however, domestic security will dwarf every other kind of federal spending: education, roads, subsidized housing, environmental protection. More than that, the decisions we make about how to protect ourselves -- the measures we demand, the ones we resist -- will take over our political discourse and define our ideas about government in the years to come.

One significant argument against the creation of an American security state, a United States that resembles Israel, is that even there, in a society rigorously organized around security, the safety of its citizens is far from guaranteed. But what keeps Israelis going about their daily lives -- and what might help Americans do the same despite the fear of violence here -- is the conspicuousness of the response and the minor sacrifices that have to be made every day. The more often we have to have our bags searched, the better we might feel. Sitting in the kind of traffic jam that would have normally frayed our nerves might seem almost comforting if it's because all the cars in front of us are being checked for bombs. We may demand more daily inconveniences, more routine abrogations of our rights. These decisions are not only going to change how we go about our days; they're also going to change our notion of what it means to be an American. How far do we want to go?

''Security is a balancing act,'' says Einav, the former El Al security chief. ''And there are always trade-offs. Give me the resources, and I can guarantee your safety. The question is, What are you willing to pay or put up with to stay safe?''

Matthew Brzezinski, a contributing writer for the magazine, last wrote about the detention of Hady Hassan Omar, a Muslim immigrant.

Copyright 2003 The New York Times Company. This text was reproduced from The New Times Sunday Magazine of February 23, 2003.