Michael Auslin writes on NRO: Years of speculation are finally giving way to some hard evidence of the Chinese government's role in cyber espionage. A new report by cyber-security firm Mandiant is making waves, including on the front page of Tuesday's New York Times. Mandiant traced the overwhelming percentage of cyber attacks on the U.S. government and American businesses and organizations to one building on the outskirts of Shanghai, occupied by People’s Liberation Army Unit 61398.

Mandiant’s report should knock the first bricks from the wall that has served, even unwittingly, to protect the Chinese government from foreign pressure over cyber-espionage. According to the Times, Mandiant discovered how Unit 61398 (or its affiliates) stole “technology blueprints, manufacturing processes, clinical trial results, pricing documents, negotiation strategies and other proprietary information from more than 100” companies that hired the firm to protect their secrets.

Yet as the Times points out, there may be even more to worry about than we supposed. Unit 61398  “increasingly [is focused] on companies involved in the critical infrastructure of the United States — its electrical power grid, gas lines, and waterworks.” A few years ago, the Wall Street Journal revealed how Chinese-origin attacks stole volumes of information on the F-35 stealth fighter’s development from subcontractors working with Lockheed Martin. China’s actions, then, have direct national-security implications.