The race to tighten the nation’s borders began just after the terror attacks on Sept. 11, 2001. Authorities learned that hijackers had lived illegally in the country, renting apartments, taking flying lessons and moving around freely. Congress demanded changes in border controls and tight deadlines for building a computer network that would screen foreign visitors as they seek to enter or leave the country by scanning their fingerprints and matching them against databases of suspected terrorists.Full Story