The United States is stepping up digital incursions into Russia's electric power grid in a warning to President Vladimir V. Putin and a demonstration of how the Trump administration is using new authorities to deploy cybertools more aggressively, current and former government officials said. In interviews over the past three months, the officials described the previously unreported deployment of American computer code inside Russia's grid and other targets as a classified companion to more publicly discussed action directed at Moscow's disinformation and hacking units around the 2018 midterm elections. In August of 2018, President Trump signed [an] executive order ... called National Security Presidential Memorandum 13. Its contents are still classified, but essentially it allows the Cyber Command to go ahead and conduct all kinds of operations inside foreign networks without going back to the president for prior approval. The first thing it did was go after those units in Russia that were responsible for a lot of the election-hacking. They went after the G.R.U., the Russian military intelligence unit that had been responsible for breaking into the D.N.C.. A lot of that ... was made public. What wasn't made public was a parallel effort to go inside the Russian power grid, to put some code in places where the Russians ... wouldn't see it, in case the U.S. ever needed to act against Russia's utilities as the Russians were putting malware in our systems.