Here's the tactic that makes China's espionage activities are so effective

As the US still attempts to formulate a response to China's massive hack of the US government's Office of Personnel Management - a breach that affected some 22 million people, including federal employees with security clearances - the massive size and scope of Beijing's intelligence gathering operations continues to come into focus.

Unlike other nations, China uses a broad array of both professional and citizen spies to gather data, Peter Mattis explains for War On The Rocks.

As Mattis describes it, the first level of Chinese intelligence-gathering resembles that of just about any other government. A Ministry of State Security carries out surveillance of targets within China and monitors potential threats, while the Ministry of Public Security has control over China's national databases and surveillance networks.

China also has various levels of military intelligence organizations within the People's Liberation Army. Most of the operatives for these organizations are also based in China, although Mattis notes that "defense attachés and clandestine collectors do operate abroad."

This also isn't all that different from how countries normally operate. The US has some 17 intelligence agencies, several of which are organized under branches of the military. They weren't under the oversight of a single Director of National Intelligence until 2005.

Where China begins to differ from other nations is its use of operatives who aren't intelligence professionals and who may technically be outside Beijing's already sprawling security sector. According to Mattis, Chinese media agencies and their foreign-based journalists have likely collected non-classified data on such sensitive topics as foreign governments' stances towards Tibet or the South China Sea. These journalists then file reports directly to the Central Committee in Beijing.

"Although most Chinese journalists are not intelligence officers and do not recruit clandestine sources, good journalists can provide information that is not publicly available, but also not classified," Mattis writes.

Mattis also describes "market incentives for economic espionage:" The process by which Beijing facilitates the theft of intellectual property from other countries by providing state support for their cover activities.

In July of 2014, Canadian authorities arrested a Chinese entrepreneur at the request of the FBI. The entrepreneur, Su Bin, and two China-based accomplices hacked into the networks of Boeing and other US defense contractors from 2009 to 2013.

Bin allegedly stole data for 32 different US projects, including data related the F-22 and the F-35 fighter jets, as well as Boeing's C-17 cargo plane. US authorities believe Bin and his colleagues tried to sell the stolen intelligence to state-owned companies within China.

China's People's Liberation Army also carries out cyber attacks and cyber espionage against US companies in order to help boost the Chinese economy. In particular, Chinese hackers have been proven to have stolen US trade secrets related to nuclear power, metal, solar production, and the defense industries.

In addition to using civilians to gather non-classified but sensitive material, Beijing has also facilitated a process for Chinese academics to gather potentially sensitive technological information, and built up institutions capable of rapidly building upon technological espionage gains.

For instance, the Institute of Scientific and Technical Information of China (ISTIC) catalogues foreign scientific publications, facilitates graduate programs for research around the world, and supports the professional development of academics throughout the country. This centralization of technological information has played an important role in China's rapid modernization, and sources tell Mattis that ISTIC likely reduced the cost of scientific research by 40-50%, while cutting research time by upwards of 70%.