New York ? Computer databases already have a lot on us: Credit cards keep track of airline ticket purchases and car rentals. Supermarket discount programs know our eating habits. Libraries track books checked out. Schools record our grades and enrollment.

On top of that, government agencies generate amass information on large cash transfers, our taxes and employment, driving history and visas, if we’re a foreign citizen.

People pass beneath a security camera on an office building in New York. David Holtzman, former chief technology officer with Network Solutions, said computers linked to cameras could one day allow profiling based on movement.

What if computers become smart enough to link all those government and commercial resources and discern patterns from people’s electronic traces? Could they help predict behavior? Prevent terrorist attacks?

One of many technology projects begun or accelerated after Sept. 11, an effort headed by former National Security Adviser John Poindexter, is trying to find out.

Such new tools are meant to make us feel safer and more secure. But they also stir concerns that we are unwittingly building a surveillance society.

The latest security-driven technologies include camera systems that compare faces with police mug shots and identification systems based on fingerprints, retinal scans or other biometrics. Already, a computerized profiling system means more screening for some airline passengers based partly on whether they paid cash or bought one-way tickets.

Individually, such technologies appear benign. But taken together, civil libertarians and some technologists say, they open the door to unprecedented intrusions into our lives.

Computers linked to cameras could one day allow profiling based on movement: “Are you walking funny? Whistling funny?,” suggests David Holtzman, former chief technology officer with Network Solutions.

Privacy concerns

We’re still a long way from a society where government tracks and records our every move. Poindexter’s work at the Defense Advanced Research Projects Agency is just that research. His group is working with simulations, deferring decisions on what databases to include and how governments would get industry’s cooperation. He acknowledges the privacy concerns and says policy-makers are beginning to discuss how to address them.

So far, potentially intrusive security measures have been limited in their use.

Identix Inc. loaned police face-recognition cameras to help scan visitors to the Statue of Liberty and Ellis Island during the Memorial Day weekend, and only a few U.S. airports, including Boston’s Logan International, have so far tried out such systems from Identix and its competitor, Viisage Technology Inc.

Controlling access

Airports and airlines, meanwhile, also have been exploring biometric ID systems to control employee access and give frequent travelers faster security clearances. But they are largely awaiting guidance and standards from the newly-formed Transportation Security Administration, which is still accepting proposals for pilot programs.

What has changed most since Sept. 11 is the threshold for tolerance among citizens.

“Things that maybe were going nowhere before Sept. 11 got a lot of push,” said Lee Tien, a staff attorney at the Electronic Frontier Foundation.

The technologies’ defenders say privacy fears often are overblown while capabilities are inadequate for monitoring and recording everybody’s whereabouts.

Nor, they say, is there interest.

But technologies have a way of starting out narrowly focused then slowly expanding in functions and capabilities.

In the San Francisco area, for instance, a system for collecting tolls electronically soon will be used to monitor motorists’ commuting patterns. A satellite positioning system designed to assist in navigation was used by a rental car company to fine drivers for speeding.

In Washington, D.C., police are linking traffic camera systems and video networks that already exist or are being installed by various public agencies. The police have about a dozen cameras now, but ultimately the system could include more than 1,000 cameras on city streets, subways and schools.

Private companies like LexisNexis, meanwhile, are trying to help government agencies perform background checks more quickly using authentication techniques developed for the financial industry.

Norman Willox, chief privacy officer at LexisNexis, said privacy concerns are valid and can be addressed by building in safeguards. But others say elected officials not technologists should be deciding how much such tools should pry.