https://www.reuters.com/article/us-usa-cyber-nsa/russian-hackers-get-u-s-cyber-defense-details-from-nsa-wsj-idUSKBN1CA2DO

Russian government-backed hackers in 2015 stole U.S. secrets on how to penetrate foreign computer networks and protect against cyberattacks after a National Security Agency contractor put highly classified information on his home computer, The Wall Street Journal reported on Thursday, citing unidentified sources.