The top U.S. intelligence official says cyberterrorism is the leading worldwide threat to U.S. security.

James Clapper is director of national intelligence. He’s telling Congress Thursday that cyberattacks and cyberspying can damage critical infrastructure like power grids. But in prepared testimony, he says advanced cyber-actors like Russia and China are unlikely to launch such attacks unless they are threatened by conflict.

He gives examples like last year’s denial-of-service attacks on websites for U.S. financial institutions, and the attack against 30,000 computers at Saudi oil company Aramco, as typical of what’s to come.

Clapper also says al-Qaida and its offshoots will continue to plot attacks on U.S. targets. He warns that the Arab Spring revolt has produced a spike in threats, and that Iran continues to present a danger.

(AP)