WASHINGTON — The National Security Agency publicly accused Russian government hackers of targeting email servers around the world in an unusual announcement on Thursday, showing that the agency is becoming more aggressive in calling out Moscow’s action as the presidential election approaches. While the Trump administration has publicly attributed cyberattacks to Russia before — including for its 2016 election hack and for paralyzing Ukraine in 2017, which damaged the operations of the

FOR NEARLY THREE years, the December 2016 cyberattack on the Ukrainian power grid has presented a menacing puzzle. Two days before Christmas that year, Russian hackers planted a unique specimen of malware in the network of Ukraine’s national grid operator, Ukrenergo. Just before midnight, they used it to open every circuit breaker in a transmission station north of Kyiv. The result was one of the most dramatic attacks in Russia’s years-long cyberwar against its western