The explosion caused the ground to tremble and glass to fly. Just before Christmas in 1983, a car bomb detonated outside London's Harrod's department store. Well-prepared U.K. shoppers, used to Irish Republican Army threats, hit the ground face-down and covered their heads. One American remained standing in the men's department, shell-shocked and unsure where to turn.

Within minutes, trained department store personnel led shoppers out of the store, urging them to evacuate the area in case a second bomb was planted nearby. Police officers, appearing from nowhere, kept everyone — except for the six dead — moving. Along the way, several blocks from the store, the injured lay on the ground, their bodies pierced by shattered glass.

In Europe, terrorism has been a way-of-life for years. But like the American in Harrod's that day, U.S. shoppers — and mall owners — have been slow to prepare. Ever since terrorists leveled the World Trade Center September 11, mall operators have been preparing for the unthinkable: a shopping center bombing.

So what are mall owners doing to reduce threats and make shoppers feel secure? They are retraining guards, installing closed-circuit television equipment, running evacuation drills, installing shock-resistant glass and redirecting traffic flow, among other measures.

Many are looking abroad and taking notes from the hard-learned lessons of other countries, especially Israel and the great Britain. So far, they've resisted the scariest and most overt measures that might frighten shoppers away, such as metal detectors, arbitrary searches and physiological profiling — but perhaps not for long.

“Nine-eleven was a terrible wake-up call, especially in the United States,” says David Levenberg, vice president of loss prevention and security at General Growth Properties Inc., which operates some 200 U.S. malls. “We've taken a number of measures to try and deter any act that might take place.” These include installing more closed-circuit television systems to maintain a constant vigil on mall activities, internally and externally. Now, about one-third of General Growth's malls feature them. Eventually, all of General Growth's regional and super-regional malls will have closed-circuit TV, Levenberg said.

The most significant change so far has been in training, Levenberg says. “Our focus is to keep the level of awareness high, whether among security staff, janitorial workers, the marketing staff or whoever,” he says. “If you see something that gives you a bad feeling you have to report it.” Guards are instructed to watch rooftops and the openings of ventilation systems for anyone trying to tamper with them.

Other measures, while not widely taken in the United States, would be easy to introduce. In Great Britain, where terrorists have targeted stores, property owners take steps to protect shoppers from car or truck bombs by installing blast-resistant glass.

“The most significant damage in approximately 75 percent of all bombings is the failure of architectural glass,” security consultant Ron Massa told Buildings magazine. One solution is to replace existing glass with laminated, shatter-proof glass or add security window film to its interior surface, says Marty Watts, president and chief executive of V-Kool Inc. in Houston, which markets security applied films. Security window film can stretch without tearing, thus absorbing much of the shock wave of an explosion. Of course, it couldn't mitigate the leveling of the World Trade Center, but it might have saved lives in recent bombings in Iraq.

Other protective steps include large planters or bollards in front of stores to keep cars a safe distance from buildings. In France, when terrorists placed bombs in public garbage cans in a series of bombings in the 1990s, authorities sealed the tops of most trashcans whenever they received intelligence that an attack might be imminent. In Great Britain, many trashcans were removed from London streets to avoid the threat entirely.

Then there's the next level of anti-terrorist measures: the Israeli-style security apparatus. This involves metal detectors at entrances, armed guards performing random searches and profiling individuals at will, among other very visible efforts to deter an attack.

“When you walk into a shopping mall center in Israel, you're under the direct scrutiny of a security officer,” says Richard Maurer, a security consultant with Kroll Inc., an international risk consulting company. “People going into a store to blow themselves up or kill people have a certain look, a tunnel vision,” Maurer says. “In Israel and England (security guards) are trained to spot that look.” That sort of expertise has prevented countless suicide bombings in Israel, according to Mauer. In many cases, “the suicide bombers never make it past the front door.”

This very visible approach is still the stuff of Tom Clancy novels. In the United States, where shopping center terrorism is still grim theory, owners are wary of turning off the public with too much visible security. In Israel and the U.K. “people are used to living with the inconvenience of security measures,” says Malachy Kavanagh, spokesman for the International Council of Shopping Centers. “We're not prepared for that.” The solution, he says, “is balancing the need for additional security measures and the public's appetite for those measures.”

General Growth's Levenberg agrees, pointing out that carrying out the types of interviews and searches that are standard in an Israeli shopping center or mall in the U.S., could even get a security guard in trouble. “We have to be sensitive in that profiling is more acceptable in other countries that it is here,” he says.

Some experts on terrorism say that mall operators should be less worried about being accused of profiling than about the threat of a terrorist bombing on their property. “Malls are disasters just waiting to happen,” says Harvey Kushner, a professor of criminal justice from Long Island University who has 38 years of experience consulting on terrorism for organizations including the Federal Bureau of Investigations, the Immigration and Naturalization Service and the U.S. Customs Service.

He accuses mall operators of not employing adequately trained security staff. “It's not enough to stick someone in a uniform and say it's all okay,” he complains. “You need better people. That's where it starts.” Levenberg says General Growth mall employees participate in “table-top” scenarios, where they're given written instructions on what to do in the even of an emergency. People have to write or explain what they do.

One way to attract better personnel is by offering higher pay and instilling the job with higher regard. “You have to motivate them, make them feel their job is meaningful” namely by hiring guards from a better educated pool and paying them better, he says. Many security jobs are, in fact, minimum wage positions.

Israeli security experts agree that the perception of a security guard's job has to be elevated from the current punch-in, punch-out mentality. Too often people here still don't “get it,” when it comes to security, he says.

U.S. malls in general are still dealing with left packages the same way they would with any lost and found item,” says Moshe Alon, president of Professional Security Consultants Corp., the top security consultant to Westfield America Trust.

“This could never happen in Israel,” he says. The key to motivating mall employees to be more vigilant isn't just a question of increasing their pay, Alon says. They have to feel they're part of the mall management team. “A guard has to feel his job is worthwhile, even the cleaning crew should feel they are part of this team that's working together” to assure the safety of the public.

“In Israel these people have pride in what they're doing,” he says. “You have to give them something to look forward to, like advancement, so that they know this isn't a dead-end job.” Alon, a former member of the Israeli secret service, would also like to see U.S. malls keep electronic blueprints of their facilities and give them to the local authorities so that, in the event of an emergency, evacuation can take place as smoothly as possible. “This will save lives,” he says.

When it comes to public security, the Israelis have become the world's undisputed experts. Their tools, including armed guards, random searches and detailed questioning — which Israel's elite security force El Al is well known for — have saved many lives in a country where terrorists have repeatedly targeted shopping centers.

In the United States, though, some worry that the constant presence of gun-toting guards or the imposition of searches and stepping through metal detectors would do more harm than good. “As a country we're not prepared to change our entire mode of living as they have in Israel,” says Jonathan Lusher, a senior vice president at IPC Security, which consults for some 400 shopping centers and malls. “There's no question that malls can be a target,” he admits, “but the type of measures taken in Israel aren't appropriate to the situation that we're in.”

Arik Arad, president and chief executive officer of Arcon Security Corp. and formerly the head of security for all Israeli shopping centers, suggests a compromise. Without bringing out the hand-held metal detectors, the machine guns and the explosives-sniffing dogs, strides can be made in keeping U.S. malls safer. The key, he says, is to train guards in the terrorist mentality. “You can use the same guards, the same energy, but they need knowledge of the terrorist modus operendi,” he says. “I would not recommend at this stage to go crazy.”

But, he says, “be prepared with a plan on the shelf,” in the event that the authorities inform the industry that the threat level has risen. “Every developer can do this.”