NEW YORK—The failed terrorist attack on New York's Times Square underscores the continued need for vigilance by risk managers and others responsible for protecting people and property, security professionals say.

Some protective steps can be taken very quickly, while others have to be done well in advance, such as the design of buildings. But nothing in the power of risk managers or building owners can eliminate the possibility of an attack, professionals warn.

Brokers, however, say the incident is unlikely to have any impact on the stand-alone terrorism insurance market (see story, page 6).

“The government cannot protect everybody, everywhere all the time,” said Yonah Alexander, director of the International Center for Terrorism Studies at the Potomac Institute for Policy Studies in Arlington, Va. “Businesses have a special obligation to protect personnel and assets.”

The question is not whether there will be an attack, “but when and where and with what impact,” said Mr. Alexander. “Basically, the worst is yet to come. It is inevitable in general.”

“This was not a car bomb in New York—it was an incendiary device,” said Neil C. Livingstone, chairman and CEO of ExecutiveAction L.L.C., a business consulting firm in Washington.

Had it detonated, there would have been “millions and millions of shards of glass, and they would have fallen on the public,” he said.

That threat can be addressed in several ways, he said. For example, buildings such as hotels could have covered walkways so glass doesn't fall on people. Also, the use of shatter-proof glass in windows facing areas such as Times Square would help, he said. “That way, it doesn't come out in millions of shards.”

Heavy drapes over windows in lobby areas can also help mitigate the exposure, he said.

Training staff to recognize possible threats is crucial, he said. “Any time you can pull a vehicle up against a building, you better know the threatening signs,” said Mr. Livingstone. He said panel trucks should be prohibited from the front of buildings and cars should be monitored.

He advised to be suspicious of vehicles with tinted windows. In addition, cars that are sagging on their springs could indicate a load of explosives, he said.

“The bigger the vehicle, the bigger the bomb,” said Hank Chase, managing principal of Frederick, Md.-based Integrity Consulting, a security consulting firm. He advocated enforcing parking restrictions around buildings.

“Keep the big stuff away from your perimeter,” he said. “The farther you can keep dangerous things away from your perimeter, the better.”

Deliveries should also be screened, he said.

Mr. Chase called detecting incendiary devices a “perplexing problem.”

“We're unable to remotely sense an incendiary device—we're decades from that,” Mr. Chase said.

Mr. Chase advised risk managers to take advantage of InfraGard, a partnership between the FBI and the private sector. “It's kind of a chamber of commerce for anti-terrorism,” he said, where law enforcement and business can share best practices. “There's no downside to InfraGard—it's just an investment of time,” he said.

“Make sure you a have credible assessment of the threat, and do whatever is necessary,” said Mr. Alexander. “Be up to the minute, up to date on the nature of the threat.”