The Chinese military shut down the Pentagon’s computer network for more than a week during an unprecedented cyber attack, according to leaked reports of an internal investigation.
China has flatly denied the allegation, dismissing it as a product of “Cold War” thinking.
However, American officials claim the People’s Liberation Army (PLA) has been implicated.
One US official told the Financial Times that an internal investigation had revealed the exact provenance of the attack in June this year, believed to be the most successful cyber attack ever carried out on the Pentagon.
The newspaper cited another source as saying there was a “very high level of confidence… trending towards total certainty” that the PLA was responsible.
Jiang Yu, a Chinese Foreign Ministry spokeswoman, said: “The Chinese government has consistently opposed and vigorously attacked according to the law all Internet-wrecking crimes, including hacking.
“Some people are making wild accusations against China … These are totally groundless and also reflect a Cold War mentality.”
A few days before the Pentagon breach, Chinese hackers were accused of infiltrating German government computers.
Angela Merkel, the German chancellor, raised the issue with China’s premier, Wen Jiabao, in a visit to Beijing and afterwards the Chinese Foreign ministry pledged to take “firm and effective action” to combat international computer hacking.
A story in the Der Spiegel newspaper claimed that the hackers had been traced to Guangzhou and Lanzhou, which are both centres of operation for the PLA.
Chinese hackers have also been implicated in cyber-espionage attempts against other governments, including that of Britain.
The PLA regularly scans US military networks and the Pentagon is widely assumed to probe Chinese networks, but US officials said the penetration in June heightened concerns because of fears China had demonstrated the ability to disrupt the network at critical times.
“The PLA has demonstrated the ability to conduct attacks that disable our system…and the ability in a conflict situation to re-enter and disrupt on a very large scale,” said a former official, who said the PLA had also penetrated the networks of US defence companies and think-tanks.