"The reality is, if you're a building owner, how can you prevent an airplane from flying into your building? You can't," says Mertz. "But you can take the threats you can do something about and build a security program around those threats and make sure your evacuation plans are up to date and ready."

Evaluating a building's security plans differs with each structure, he says. Larger government buildings, arenas and public facilities require greater scrutiny while smaller properties may simply need to update existing security measures.

The terrorist threat also has created a need for terrorist insurance for larger projects, Mertz emphasizes. Lenders now require many builders to take out the specialty insurance before they can get a loan at rates that Mertz estimates could add 20% to 30% to a builder's insurance premium.

On smaller projects, security is a concern as well. Jackque Chilton, a property manager with CB Richard Ellis Inc. in Phoenix, tells GlobeSt.com that the effects of the terrorists' attacks coupled with a tumbling economy have created an acute awareness of security among tenants who have seen a spike in burglaries and robberies. "What we're seeing is that tenants have become more aware of their surroundings," she says. "Now, if they see something suspicious, they will call" the police or the property manager.

One positive effect of the disaster, however, has been that tenants are now working together to solve common problems, Chilton says. "There's been a community effect," she notes. "Tenants are communicating more than they used to."

But with the anniversary of the attacks, there remains some apprehension among owners and tenants. "Like everyone else, we're just holding our breath as we go through this first anniversary and hoping we go through it without incident," Mertz concludes.