In the report to Congress, based on the assessment of 14 U.S. intelligence agencies, the Office of the National Counterintelligence Executive said the two countries protect their anonymity by using proxy computers and routers in third countries, The New York Times said.
"The computer networks of a broad array of U.S. government agencies, private companies, universities and other institutions -- all holding large volumes of sensitive economic information -- were targeted by cyberespionage," the report stated.
The report, focusing on foreign economic and industrial spying in the past two years, indicated China and Russia are the leaders in Internet theft of economic secrets.
"Chinese actors are the world's most active and persistent perpetrators of economic espionage," the report said.
"Russia's intelligence services are conducting a range of activities to collect economic information and technology from U.S. targets."
The countries contract with independent hackers to widen their spying ability and to hide responsibility, the report said.
The study said most of the cyberspying aimed at American economic targets has focused on information and communications technology; assessments of supplies of scarce natural resources; technologies for clean energy and healthcare systems or pharmaceuticals; and military information, particularly maritime systems, unmanned aerial vehicles and airplane and space technologies.
Notable deaths of 2014 [PHOTOS]