The U.S. counterintelligence head says the list of threats is long and getting longer

As the head of American counterintelligence, Mike Casey sees on a daily basis the scope of foreign spying operations, cyberattacks and economic espionage against the United States.

"The scale is impressive and terrifying," said Casey, who stepped into his current job last year after working for more than two decades in Congress. He finished up his time on the Hill as the staff director for the Senate Intelligence Committee, so he already had deep understanding of the array of threats facing the U.S.

What's changed now, though, is it's his responsibility to keep those secrets safe.

"Fortunately for me, and unfortunately for everybody else, counterintelligence, it turns out, is a growth business," he told NPR in an interview. "More players are getting into it with more tools, going after more targets."

The list of concerns is a long one. The usual suspects — China, Russia, Iran and North Korea — lead the way, he says, but there are other actors, including private sector entities and cybercriminals who are also getting involved.

"It's not just the Russians stealing secrets from the State Department anymore," Casey said. "It's everybody trying to steal all sorts of intellectual property, going after critical infrastructure. Just the list goes on and on."

For all the changes, one foreign adversary still stands out, he says, for the ambition and scale of its espionage efforts against the U.S.: the People's Republic of China.

The kinds of U.S. targets China goes after

Casey says Beijing has studied American history and has concluded that the U.S. achieved greatness, in part, by helping craft the world system that emerged from the ashes of World War II and the rules that govern it.

"And they have a view of national