And Chinese targeting of U.S. scientific and business is a multi-pronged attack, targeting business and science.

In the DOJ statement on Zheng, the FBI's Alan Kohler Jr said China was targeting "American ingenuity" and seeking to "topple our status" as global leader. Zheng was an engineer specialising in turbine sealing technology and worked on various leakage containment technologies in steam turbine engineering. Such seals optimise turbine performance "whether by increasing power or efficiency or extending the usable life of the engine", the DOJ said. Gas turbines that power aircraft are central to the development of China's aviation industry. Aerospace and aviation equipment are among 10 sectors that the Chinese authorities are targeting for rapid development to reduce the country's dependence on foreign technology and eventually surpass it. But Chinese industrial espionage is targeting a wide range of other sectors too. According to Ray Wang, founder and CEO of Silicon Valley-based consultancy Constellation Research, they include pharmaceutical development and nanotechnology - engineering and technology conducted at the nanoscale for use in areas such as medicine, textiles and fabrics and automobiles. A nanometre is a billionth of a meter. It also includes pharmaceuticals, bioengineering - mimicking biological processes for purposes such as the development of biocompatible prostheses and regenerative tissue growth. Mr Wang cited an anecdote by a former head of research and development for a Fortune 100 company, who told him that "the person he entrusted the most" - someone so close that their children grew up together - was eventually found to be on the payroll of the Chinese Communist Party. "He kindly explained to me that the spies are everywhere," he said. In the past industrial espionage from countries such as Japan, South Korea, Taiwan and Singapore was a concern, Mr Marro said. However once indigenous firms emerge as innovative market leaders in their own right - and so start to want to protect their own intellectual property - then their governments start passing legislation to take the issue more seriously. "As Chinese firms have become more innovative over the past decade, we've seen a marked strengthening of domestic intellectual property rights protection in tandem," Mr Marro said. There have been attempts to rein in hacking specifically. In 2015 the US and China struck a deal in which both sides pledged not to carry out "cyber-enabled theft of intellectual property, including trade secrets or other confidential business information for commercial advantage". By the following year, the US National Security Agency had accused the Chinese of violating the agreement, although it did acknowledge that the quantity of attempts to hack government and corporate data had dropped "dramatically". But observers say the deal's overall impact has been minimal. Mr Wang said it was a "joke" due to a lack of enforcement. Chinese cyber-espionage in the US has been "pervasive" and extends to academic labs. "It has been going on in every aspect of Western businesses," he told the BBC. However Lim Tai Wei from the National University of Singapore noted that there were no "definitive uncontested studies" on the extent of the phenomenon. "Some believe that there was a short dip in Chinese cyber espionage against the US, but resumed its former level thereafter. Others believe it failed due to the overall breakdown in US-China relations," he said. Meanwhile the US is now directly trying to block China's progress in the key semiconductor industry - vital for everything from smartphones to weapons of war - saying China's use of the technology poses a national security threat. In October, Washington announced some of the broadest export controls yet, requiring licences for companies exporting chips to China using US tools or software, no matter where they are made in the world. Washington's measures also prevent US citizens and green card holders from working for certain Chinese chip companies. Green card holders are US permanent residents who have the right to work in the country. The US is beating China in the battle for chips Mr Marro says that while these measures will slow China's technological advance, they will also accelerate China's efforts to remove US and other foreign products from its tech supply chains. "China has been trying to do this for years, with muted success, but these policy goals now command greater urgency as a result of the recent US controls," he said. With China also invoking its own national security, the scramble for a technological edge between the world's two biggest economies is only likely to intensify further. But Mr Wang reckons that the US still holds the advantage. "My cyber-security friends tell me when they hack Chinese sites, the only worthwhile tech [they can find there] is US intellectual property," he said.