According to a US intelligence report, China and Russia are the most active perpetrators of economic cyber-espionage against US companies.
The report has specifically cited Chinese "actors" and Russian intelligence as the top culprits.
According to Robert Bryant, US national counter-intelligence executive, who spoke to reporters, online spying was a quiet menace to the US economy.
The allegations have been denied by embassies of both China and Russia.
According to the report, titled Foreign Spies Stealing US Economic Secrets in Cyberspace, both private firms and cybersecurity experts had reported an "onslaught" of computer network intrusions originating from China.
However, the real culprit remains untraced. According to Google's statement in 2010, it had suffered a data loss from attacks by Chinese hackers.