correctionA previous version of this article incorrectly asserted that, in leaked documents, the Chinese hacking group iSoon claimed to be able to exploit vulnerabilities in U.S. companies, including Microsoft, Apple and Google. In fact, the hackers claimed that they were able to target users of these platforms to install malicious software and extract data. The article has been corrected.A trove of leaked documents from a Chinese state-linked hacking group shows that Beijing’s intelligence and ...