The US and China have launched a war of words over allegations made by a US congressional panel that Chinese government-linked hackers had launched dozens of cyberattacks on American defence contractors.

Beijing has flat-out denied the charges, saying they were "fabricated out of thin air." According to the Senate panel released a study a day prior, hackers had gained access to systems run by companies doing contract work for the US Transportation Command (Transcom) at least 50 times between 2012 and 2013, potentially compromising military operations. "Chinese law prohibits cyberattacks and other crimes, and cracks down on such crimes," Chinese foreign ministry spokesman Hong Lei said. "The Chinese government and military will never support hacker attacks." "The accusation against China is fabricated out of thin air, and is groundless," he added. "We urge the American side to stop its irresponsible accusations against China." The US has made similar accusations as recent as this May. Chinese authorities banned the use of Microsoft's Windows 8 operating system on all new government computers and suspended activities of a bilateral cyber-working group.

Following which a US grand jury indicted five Chinese military officers on charges they broke into US computers to benefit Chinese state-owned companies, in the first-ever prosecution by Washington of state actors over cyberespionage, AFP reported in May.

The New York Times in July quoted US officials saying Chinese hackers accessed US government computers containing personal information on all federal employees. According to AFP, the Senate Armed Services Committee's report found that of the 50 attacks, at least 20 were "attributed to an 'advanced persistent threat' (APT), a term used to distinguish sophisticated cyber threats that are frequently associated with foreign governments." The hacking has apparently occurred for years.

Between 2008 and 2010, for example, a "Chinese military intrusion" into a Transcom contractor compromised emails, documents, computer code and passwords, the report said.