Jan. 24 (Bloomberg) -- The Bush administration's domestic spying effort is needed to prevent terrorist attacks in the U.S., Attorney General Alberto Gonzales said in seeking to counter criticism of the program.

Gonzales, speaking at Georgetown University's law school in Washington, argued that President George W. Bush had authority from Congress and the Constitution to set up the program. About 25 law students silently protested during the half-hour speech, turning their backs on Gonzales and holding up a sign saying: ``Those Who Would Sacrifice Liberty for Security Deserve Neither.''

Gonzales didn't acknowledge the students, several of whom put black pillowcases over their heads. The attorney general cited new threats by al-Qaeda leader Osama Bin Laden and said Bush would continue to authorize the eavesdropping to protect U.S. citizens.