The scale of China's espionage activities is unprecedented, sources told The Wall Street Journal.
China has mobilized security agencies, private companies, and Chinese civilians in its espionage activities with the goal of boosting its economy and undermining rival states, the Journal reported.
Last month, the FBI reported a Chinese firm hacked 260,000 internet-connected devices in the U.S., Britain, France, and other countries. Chinese cargo cranes used at U.S. seaports have embedded technology that could allow China to control them, according to a congressional probe.
Western spy agencies have said they are unable to contain China's espionage, the Journal reported. They are telling businesses and individuals to be on alert about any interactions with China.
According to the FBI, Chinese hackers outnumber the agency's cyber personnel 50 to 1. A European agency estimated China's intelligence gathering and security operations might have up to 600,000 people, the Journal said.
In September, federal U.S. prosecutors claimed five Chinese University of Michigan graduates were discovered in the middle of the night taking photos near military vehicles in a National Guard training exercise that included Taiwan military personnel, the Journal reported.
The U.K. alleged Chinese-linked hackers had accessed the country's voter registration records while the U.S. is investigating whether a Chinese hacking group broke into U.S. broadband providers, accessing wiretaps.
The FBI alleged China hijacked routers to infiltrate American water and energy networks, and in December, Congress banned the Pentagon from using any seaport worldwide that deploys the Chinese cargo-data platform Logink, out of fear classified information could be disclosed, the Journal reported.
China's intelligence operations are decentralized, making it difficult for Western countries to spy on China, the Journal said. Its intelligence operates largely autonomously, making the system difficult to penetrate, and their methods appear haphazard, according to the Journal.
In 2014, the U.S. attempted to keep China in check by imposing tariffs and attempted to stop European allies from using Chinese software to build its telecom infrastructure after accusing China of digging through American corporate secrets through hacking, the Journal reported.
China has regularly denied it spies on Western countries.