But CNCERT said in a statement that it had not received any reports of a security incident from the University of Toronto, where some of the researchers behind the Shadow report are based. The reason for the contradictory statements was not immediately clear.
"During our investigation, we recovered documents that are extremely sensitive from a national security perspective as well as documents that contain sensitive information that could be exploited by an adversary for intelligence purposes," the report said.
Several documents recovered were labeled "secret," "restricted," or "confidential" and originated from India's National Security Council Secretariat and Indian embassies abroad.
In addition, the Shadow network targeted Indian academics and journalists with a "keen interest" in China, the report said, citing the recovery of stolen documents discussing Chinese military exports, Chinese policy on Taiwan and Sino-Indian relations, as well as other topics related to China.
The Shadow network also collected personal information on individuals belonging to Indian government and military organizations that could be used in future attacks, it said.
The report concludes that Shadow was controlled from China and attributes responsibility for the network to "one or more individuals with strong connections to the Chinese criminal underground." However, it didn't rule out the possibility of a connection between these individuals and the Chinese government.
"Given the often murky relationships that can exist between this underground and elements of the state, the information collected by the Shadow network may end up in the possession of some entity of the Chinese government," it said.
(Owen Fletcher in Beijing contributed to this report.)