National Intelligence Director James Clapper says terrorists have "gone to school" on U.S. surveillance efforts following Edward Snowden's information leaks.
Clapper told a U.S. Senate Intelligence Committee because of the former National Security Agency contractor's leaks terrorists have changed their communication methods, making the intelligence community's work more difficult.
During testimony Wednesday, Clapper called the leaks the “most massive and damaging theft of intelligence information” in American history, begging Snowden to return unreleased documents.
“Terrorists and other advisories of this country are going to school on U.S. intelligence sources, methods, and tradecraft, and the insights they are gaining are making our job much, much harder,” he said.
“Snowden claims he has won, and his mission is accomplished," Clapper added. "If that is so, I call on him and his accomplices to facilitate the return of the remaining stolen documents that have not yet been exposed to prevent even more damage to U.S. security.”
National Counterterrorism Director Matthew Olsen also told the committee there has been an “uptick” in terrorist threat reports before the Winter Olympics next week in Sochi, Russia.
“This is what we expected, given where the Olympics are located," he said. "There are a number of extremists in that area; in particular, a group, Imirat Kavkaz, which is probably the most prominent terrorist group in Russia.”
Olsen said the greatest threat is not to the athletes or spectators within the venues at the Olympic Games.
“There is extensive security at those locations, the sites of the events. The greater threat is to softer targets in the greater Sochi area and the outskirts, beyond Sochi, where there is a substantial potential for a terrorist attack," he said.
During the annual hearing on current and projected U.S. national security threats at home and abroad, Committee Chair Dianne Feinstein said Syria is a growing concern for terrorists.
"I think the most notable development since last year’s hearing is actually in Syria, which has become a magnet for foreign fighters and for terrorist activities," said Sen. Feinstein (D-Calif.). "The situation has become so dire that even al Qaida’s central leader, Ayman al Zawahiri, has renounced the activities of one group as being too extreme.”
The committee also expressed concern about Afghanistan, saying it cannot lose a “must-win” war in the country.