The code detected in the northeastern state's system did not disrupt its operations, the paper cited US officials as saying.
The code was associated with the Russian hacking efforts that US officials have dubbed "Grizzly Steppe."
Russian central bank loses $31 million in cyber attack
US authorities have not yet pinpointed why the Russians targeted the grid, according to the Post, but that it "may have been designed to disrupt the utility's operations or as a test by the Russians to see whether they could penetrate a portion of the grid."
In December 2015, a power failure that plunged parts of western Ukraine into the dark was found to be caused by a cyberattack. The Russians were accused of causing the blackout, an allegation they have denied.
Cyber attack likely mitigated, US Homeland Security says
A US federal law enforcement report released this week showed that Russian intelligence agencies over the last two years blanketed Democratic Party targets with malicious emails and have likely continued such efforts after November's elections.
The report's release followed an array of measures unveiled by Washington as retribution for what American officials have described as Moscow's malicious efforts to tip the vote in favor of President-elect Donald Trump by stealing embarrassing information from Democratic Party operations and senior party members before releasing it to the news media.
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