NEW YORK (Reuters) - As long-haired computer programmers and bearded civil liberties advocates gathered in a hotel ballroom on Wednesday, it was the clean-shaven Army guards at the train station across the street who evidently dominated the agenda.

Past sessions of the Computers, Freedom and Privacy conference have tackled government technology policies, including encoded communications and online privacy. But participants said anti-terrorism efforts appear to be the top concern this year.

"You can have as much security as you want. It's just a question of what you are willing to give up for it in return," said computer security expert Bruce Schneier.

From weakened wiretap laws to airline passenger-screening programs that check bank records and other personal data, domestic security efforts have shifted the agenda, said conference organizer Barry Steinhardt, with the heightened military presence around the city only the most visible change.

"New York has, to some degree, the feel of an armed camp," Steinhardt, associate director of the American Civil Liberties Union, said in welcoming conference attendees.

Speakers questioned what impact security efforts will have on personal liberties and whether those efforts would be effective at preventing attacks.

ANTI-TERROR AGENDA CHANGING SOCIETY?

Every government dollar devoted to anti-terror efforts is a dollar not spent fighting crime, disease or other threats, they said. At the same time, private businesses could use security as an excuse to further their own agendas -- prohibiting sports fans from bringing coolers into a baseball stadium, for example.

The new efforts will inevitably lead to abuses of power if unchecked, speakers said.

"Privacy-invasive measures being developed right now would have been considered unthinkable a few years ago in Western countries," said George Radwanski, the Canadian government's privacy commissioner. "What we are confronting is a permanent redefinition of our societies."

The conference covers a range of topics -- from the growing use of video surveillance cameras in public spaces to the potential abuses of embedded radio frequency chips by retailers to thwart theft.

While the conference has included national intelligence and Department of Justice officials in the past, this year there were few government representatives listed on the program. Most officials had declined to participate, Steinhardt said, saying they were occupied with other matters.

Analysts from conservative think tanks like the Heritage Foundation stepped in to defend surveillance programs like the Defense Department's Total Information Awareness "data mining" effort, but they found few allies either on the podium or in the audience.

As a result many discussions took the form of motivational pep talks rather than no-holds-barred debate.

'HEAVY BURDEN'

"We have a heavy burden on us here. We are fighting, in our way, an asymmetrical war," said Jim Dempsey, executive director of the nonprofit Center for Democracy and Technology.

Dempsey said privacy advocates need to renew their old alliance with the business community, which in the 1980s sought to limit government access to their customer lists and purchase records, and reach out to Arab-Americans and immigrant communities facing increased surveillance.

Security fears reduced attendance even among committed computer civil-liberties activists, several organizers said. Some potential participants stayed at home, citing fears of traveling during wartime.

"In prior years, people were caught up in all the ways technology could fix social problems. What we are seeing now, with focus on security, is that technology is fixing things, but in the wrong direction," said Robert Guerra, an international human rights campaigner from Canada and one of the conference organizers.

Among the scheduled events is a panel that will seek to expose "Stupid Security" technologies that fail to accomplish their stated goals, as well as the distribution on Thursday of Privacy International's "George Orwell Awards" -- mock prizes for the biggest violators of citizen and consumer privacy rights among government officials and corporations as judged by a panel of privacy rights advocates. (Additional reporting by Eric Auchard)