Residential landlords say they've been alert for years.

In the wake of recent terrorism alerts, residential landlords in New York City are trying to use caution, but many say the preventive measures recommended by the FBI and the NYPD have been implemented by management companies long before Sept. 11.

The alerts, which mention the possibility of Al Qaeda operatives planting explosives inside large apartment buildings, have prompted law enforcement officials to recommend thorough background checks for any prospective tenants. But according to Doug Weinstein, vice president of operations for AKAM Associates, background checks are nothing new when it comes to New York.

"Most of the things the FBI has suggested we have been doing all along, but when you hear it from someone in law enforcement it gives it more weight," he said. "Most of it has to do with just being aware of anything suspicious."

AKAM, as well as other New York landlords, began implementing stricter security measures recently, including a "no waiting in the lobby" policy for building visitors and checking of all incoming packages.

"We've sent out notices to all home owners regarding new rules on access into the building and we are encouraging the garage operators to look inside the cars to ensure nothing suspicious is bidden inside," said Neil Bender, of Bellmarc. "We always required a rather extensive background check before accepting anyone as a tenant, but now we are much more aware of people who are foreigners. This is something we never did before."

But another source, whose company attended the security conference organized by the NYPD last week, said that apartment building tenants are not likely to see dramatic changes in their landlords' behavior.

"All of the things they have talked about -- background checks, credit checks, we have been doing for a long time," he said. "We have been in business for a long time -- we are not going to let just anyone rent an apartment for cash from us."