The Mandiant report, which was released last week, traced a series of cyberattacks to a 12-story building in Shanghai. The private security analysts concluded that the building, which likely holds hundreds or even thousands of employees, is almost certainly the headquarters of China's secretive cyber war division, the People's Liberation Army Unit 61398.
Mandiant wrote that since 2006, the Chinese hackers have stolen data from at least 141 companies across 20 major industries, including critical infrastructure sectors like energy and telecommunications. At least 115 of the companies were in the United States.
China has denied the accusations.
The Obama administration has said that many cyberattacks are coming from China, but has yet to explicitly accuse the Chinese government of carrying out the attacks.
"Chinese actors are the world’s most active and persistent perpetrators of economic espionage,” the White House wrote in a recent report on trade secret theft. “US private sector firms and cybersecurity specialists have reported an onslaught of computer network intrusions that have originated in China, but the [intelligence community] cannot confirm who was responsible."
For more on Feinstein's comments, click here.