Travelers to and from the United States are encountering increased security measures designed to weed out potential terrorists. There are tightened visa screening procedures and new electronic controls on passports. But a team of information technology researchers at the University of Maryland says there is a wider range of counter-terrorism technologies still in development.

A few months ago, Senator Ted Kennedy was about to take a plane from Washington to his home state of Massachusetts. It was a ride he'd done hundreds of times during his four decades in Congress.

But this time was different, very different. Security officers would not allow him to board the commuter flight. When his name flashed on the computerized passenger list, there was an alert that warned airline agents to check the passenger again.

The new name identification technology was developed by hi-tech companies that compile databases with all possible combinations and spellings of names of terrorist suspects.

The alert on Mr. Kennedy proved to be a mistake, but others have not. Security analysts say the complex databases do help screen suspicious travelers.

The security business has grown considerably in the wake of the 2001 terrorist attacks. So has research into new and improved ways of tracking suspects.

William Lahneman is program coordinator of the Center for International and Security Studies at the University of Maryland. He says the intelligence community must adapt its tools to provide to changing threats.

"Given the point the threat itself has probably changed, I think we can agree in the last ten years, trans-national terrorism has changed, [and] the tools available to the counter terrorism forces have also changed," he says. "And in a general way, the general threat environment, the globalization has changed as well. It would make sense that the individual analyst in the intelligence community should also change."

One example of that changing focus is electronic surveillance. Computer expert Rama Chellapa of the University of Maryland is researching ways to enhance human security operations with electronic sight, as he calls it, to detect unusual behavior.

"When people want to do nasty things, they want to make it appear like it's normal thing," adds Mr. Chellapa. "So it's very difficult to tell normal behavior from abnormal behavior."

Mr. Chellappa is monitoring how people walk to see if he can detect patterns indicating a potential suicide bomber. He says the technology could be applied to public security cameras, especially in sensitive locations like banks or government buildings.

Prevention is also a major focus of counter-terrorism work on the computer.

Lee Strickland of the University of Maryland's College of Information Studies talks about combing the increasing number of radical Web sites on the Internet to detect clues of possible attacks being planned.

"Most of us are generally familiar with the use of the Internet by terrorist organizations," he says. "Publicity, very cheap very visible, astonishing reach and purposes of recruitment as well as general propaganda. Also, a secret communications tool to communicate with agents in place or cells in distant lands. Third, secret financial channel from fund-raising to money laundering. An instrument of intelligence gathering. A tool of terrorism to disrupt critical infrastructure, cyber terrorism. And lastly, simply a tool to instill fear in the population in the real world and the virtual world."

Information systems analyst James Hendler says the primary focus of counter-terrorism research must be prevention.

"What I think is most important and just starting to permeate the thinking of our country is we must move from a view of terrorism as something we react to and move to a view of terrorism as something we prevent," he notes. "Much of the research pre-9/11 and even for a couple of years after has been more focused on how do we survive a terrorist attack. How do we build a capability to prevent this?"

Mr. Hendler says prevention depends on information sharing at home and abroad by intelligence technology researchers and government security agencies.

A lot of the preventative measures under study or already in operation have raised concerns about civil liberty abuses, from electronic surveillance to computer and telephone intercepts.

William Lahneman says the American public has shown a surprising willingness to weigh the trade-offs.

"The American people want the necessary privacy in keeping with the threat," explains Mr. Lahneman. "So if the threat goes up, polls seem to indicate they are willing to surrender some of that privacy and if the threat goes down then privacy becomes more important. So it's a sliding scale."

Researchers are aware of the potential for abuses in developing more potent counter-terrorism security. Balancing new levels of security with the need to safeguard civil liberties, they say, will be the responsibility of the policy-makers.