The report by Mandiant identified the People's Liberation Army's Shanghai-based Unit 61398 as the most likely driving force behind the hacking. Mandiant said it believed the unit had carried out "sustained" attacks on a wide set of industries.
"The nature of 'Unit 61398's' work is considered by China to be a state secret; however, we believe it engages in harmful 'Computer Network Operations'," Mandiant said in the report released in the United States on Monday.
"It is time to acknowledge the threat is originating in China, and we wanted to do our part to arm and prepare security professionals to combat that threat effectively," it said.
China's Defence Ministry did not immediately respond to faxed questions about the report on Tuesday.
Unit 61398 is located in Shanghai's Pudong district, China's financial and banking hub, and is staffed by perhaps thousands of people proficient in English as well as computer programming and network operations, the report said.
The unit has stolen "hundreds of terabytes of data from at least 141 organisations across a diverse set of industries beginning as early as 2006", it said.
Most of the victims were located in the United States, with smaller numbers in Canada and Britain. The information stolen ranged from details on mergers and acquisitions to the emails of senior employees, the report said.
The Chinese government has consistently denied being involved in such activities. Experts scoff at the denials.
"The PLA plays a key role in China's multi-faceted security strategy, so it makes sense that its resources would be used to facilitate economic cyber espionage that helps the Chinese economy," said Dmitri Alperovitch, chief technology officer and co-founder of CrowdStrike, one of Mandiant's competitors. - Reuters
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