The Trump administration is preparing to conduct aggressive action against foreign nations that hit the United States with cyber attacks, a White House policymaker said Thursday.

Tom Bossert, assistant to the president for homeland security and counterterrorism, said China, Russia, Iran, and North Korea have not been deterred from conducting cyber attacks using the internet.

“They are right now not paying enough—they’re not paying anything,” Bossert said, noting that sub rosa cyber actions, whether stealing data or destroying computer systems, are “a very cheap exercise from them and a very high reward.”

The first step in a new cyber policy being drawn up by the White House is to better protect American infrastructure—such as the electrical grid and financial networks—from attack, Bossert told a security conference in Aspen, Col.