America's collective sense of security changed dramatically after terrorists attacked the United States on September 11, 2001. Many Americans now feel vulnerable, not only to more attacks, but to new measures meant to prevent terrorism.
Travelers in the United States have faced heightened security at airports for the past 10 years.
Some measures still stir controversy, but for traveler Bob Dubois, they are necessary.
"I think it's something that we need in this day and economy as it is right now with what's going on," Dubois said. "You never know what's going to happen and the people that are out there, and I think that we need to do this."
Oscar Del Castillo agrees the new measures are needed.
"A few procedures, I'm not entirely pleased with, such as the full-body scans," he says. "However, I understand their importance."
Ameena Mirza Qazi, an attorney with the Council on American-Islamic Relations in Los Angeles, complains that the heightened procedures target observant Muslims.
"When I travel, I get pulled over almost every single time I go through security for extra pat-downs because of my head scarf," she says.
Although transportation security officials say they do not specifically target Muslims, many Muslims say they suffer discrimination. Last year, a mosque near San Diego faced neighborhood protests over its plans to expand.
Civil rights advocates sued the Federal Bureau of Investigation earlier this year for allegedly using informants to monitor Muslims. FBI officials would not comment, but they say they take action only when they suspect criminal behavior and that agents operate under strict guidelines.
Ahilan Arulanantham of the American Civil Liberties Union says those guidelines are too broad and intrusive. He says the nation's founding fathers lived in a time of turmoil after the revolutionary war and intended that basic rights enshrined in the constitution be sacrosanct.
"And the rules that they created were designed to protect us and strike that balance even during that time," Arulanantham explains.
Steven Martinez of the FBI's Los Angeles office says the United States remains committed to an open society, but the risk of terrorism is real.
"If we want to maintain that sense of freedom, we’re always going to have vulnerabilities in places where people gather - theme parks, movie theaters, shopping malls," notes Martinez. "Those present opportunities for our adversaries and those are very, very difficult to secure."
Security expert Erroll Southers of the University of Southern California says Americans need to face, and manage, the new risks.
"The same as they're told about the challenges we have with earthquakes, fires, floods, hurricanes," Southers says. "This is a disaster of a man-enabled paradigm, so we should be educating them on what the real threats are. And then second, we should make sure they understand how they can help."
Southers says tips from the public are crucial in stopping terrorists, but effective security measures still must respect the rights of Americans. Finding the right balance is the hard part.