Despite a cyber-warfare truce, one defense analyst said China is probably still engaged in the theft of sensitive U.S. military technology. Hacking over the years is one of the reasons China has been able to narrow the gap with the U.S. in advanced missiles, drone technology and even stealth aircraft.
Also, a report predicts that by 2030 the Chinese could dominate artificial intelligence and exploit it for military purposes.
For example, when China wanted to build the J-20, a new stealth fighter jet, they were reportedly helped by industrial espionage. The J-20 became operational in September.
There were said to be several prototypes of the plane, but the final sleek design resembles the F-22, a stealth fighter made by Lockheed Martin. China's smaller stealth fighter, called the FC-31 Gyrfalcon, in development is seen as a knockoff of Lockheed's F-35.
"What Beijing has been very good at is targeting U.S. defense contractors, getting into their computer systems through various types of essentially cyber warfare and stealing the designs of some of America's best military assets," said Harry Kazianis, director of defense studies at the Center for the National Interest, a think tank founded by former President Richard Nixon.
Although a U.S.-Chinese cyber-hacking truce was announced in 2015, Kazianis and others remain skeptical it will matter over the long term. He says China could have agents in other countries still doing hacking or "camouflage" such activity through various methods.
"So we don't even have a good idea if they stopped," he said. "It's obviously a huge, huge problem."
According to Kazianis, the Chinese have been able to hack into computer networks to steal designs and other information on U.S. carriers, advanced defense systems as well as the F-22 and F-35 jets.
Indeed, a federal grand jury in 2014 indicted a Chinese national for a computer hacking scheme that involved the theft of trade secrets from Boeing's C-17 military transport aircraft. The individual, who last year entered a guilty plea, also was accused of working with two co-conspirators based in China to steal military data about the F-22 and F-35 jets.
The concern is China's supersonic J-20 could one day become a threat to the F-22 and the smaller F-35 fighters.
The Center for Strategic and International Studies, a think tank based in Washington, said Beijing's "J-20 has the potential to considerably enhance China's regional military strength."
For one, the J-20's could give China an advantage should it want to use the warplane in a dogfight with the U.S. or allies. Also, depending on its stealth capabilities, the J-20 could be used for strikes on Taiwan or U.S. airbases.
Then again, the J-20's design may make it susceptible to detection. It features angles that allow it to deflect radar emissions from the front but reports suggest its signature reduction falls short elsewhere. Portions of the J-20's engines also "may work against its stealth capabilities," according to CSIS.
"Almost every fighter in the world has some kind of emissions that come out with radar or communications devices just like radios that we can detect," said John "JV" Venable, a senior research fellow for defense policy at the Heritage Foundation, a Washington conservative think tank. "When we can pick those [emissions] up, then we can actually find, fix and kill that fighter."
Venable, a retired Air Force colonel, said the U.S. military's ability to "mask emissions is very good, and our ability to detect is very good. We just don't know what theirs is [with the J-20]."