Investigators said they have identified a secretive hacking group that has spent years systematically targeting US partners in the space and satellite industry, most likely on behalf of the Chinese military.

The group typically gains a foothold in sensitive networks by attaching booby-trapped documents to e-mails, according to a 62-page report published Monday by Crowdstrike, a firm that conducts forensic investigations on behalf of customers who have suffered security breaches. When employees click on the documents, the attackers are able to gain control over their PCs. The attackers then use the PCs to take control of servers housing blueprints, customer lists, or other sensitive data. The group, dubbed as Putter Panda, is connected to Unit 61486 of the People Liberation Army's (PLA's) Third General Staff Department, according to the report.

"Putter Panda is a determined adversary group, conducting intelligence-gathering operations targeting the Government, Defense, Research, and Technology sectors in the United States, with specific targeting of the US Defense and European satellite and aerospace industries," Crowdstrike researchers wrote. "The PLA ’s GSD Third Department is generally acknowledged to be China’s premier Signals Intelligence (SIGINT) collection and analysis agency, and the 12th Bureau Unit 61486, headquartered in Shanghai, supports China’s space surveillance network."

The report is the latest to charge the Chinese military with supporting a comprehensive espionage campaign targeting key US intelligence. Last year, Crowdstrike competitor Mandiant documented the activities of Unit 61398, a PLA-sponsored hacking group that had siphoned terabytes of sensitive data from 141 organizations in the previous seven years. Last month the US Justice Department formally charged five members of Unit 61398 with hacking US companies and stealing their trade secrets. Chinese officials have denied claims it sponsors hacking and has countered with claims the US is behind its own set of hacks.

According to Crowdstrike, one of the attachments Putter Panda used to infect its targets appeared to be a brochure for a yoga studio in Toulouse, France, a hub of the European aerospace industry. End users who opened the document on unpatched computers were then infected. Although Unit 61486 members are secretive, they have occasionally disclosed their ties to the Chinese military, the Crowdstrike report asserts. In one case, an Internet domain used to launch an attack was registered with an e-mail address belonging to a student at the School of Information Security Engineering at Shanghai Jiao Tong University, which has long been a suspected recruiting ground for the Chinese military. Another domain was registered with an e-mail address used by a 35-year-old who listed the military as his profession.