FOREIGN governments and companies have long suspected that the Chinese hackers besieging their networks have links to the country’s armed forces. On February 19th Mandiant, an American security company, offered evidence that this is indeed so. A report, the fruit of six years of investigations, tracks individual members of one Chinese hacker group, with aliases such as Ugly Gorilla and SuperHard, to a nondescript district in residential Shanghai that is home to Unit 61398 of the People’s Liberation Army. China has condemned the Mandiant report. On February 20th America announced plans to combat the theft of trade secrets.