When the New York Times revealed that it had been attacked by Chinese hackers last month, after publishing details of premier Wen Jiabao’s family assets, Beijing furiously rejected suggestions of involvement. Yet a new investigation into cyber attacks on western companies has gravely undermined China’s repeated denials that it supports such activity.

Mandiant, a web security consultancy, has spent years tracking cyber attacks on business. Its lengthy report sets out details of what it believes are sustained assaults by a group of hackers known as APT1, who bear an uncanny resemblance to a unit of the People’s Liberation Army. Though the evidence is short of damning, the report goes further than others in linking the military to offensives on foreign companies.

Globally, cyber attacks are on the rise. According to Akamai, which monitors web activity, the percentage of assaults originating in China doubled between the second and third quarters of 2012. But it is not the only culprit. US intrusions ranked second and Russian third. Cyber warfare is now one of the world’s top five security threats – and everyone is at it.