The Clinton team expressed concern throughout the campaign that the Republican was a "puppet" of Vladimir Putin and that the Kremlin was, at the very least, condoning hacks if not supporting them.
The Washington Post reported CIA sources as saying the agency now believes it has evidence individuals with connections to the Russian government was behind a number of hacks targeting the Democrats.
The officials described the hackers as people known to the intelligence community who were part of a wider Russian operation to boost Trump and reduce Clinton's chances of winning the election.
"It is the assessment of the intelligence community that Russia's goal here was to favor one candidate over the other, to help Trump get elected," the Post quoted a senior U.S. official as saying.
"That's the consensus view."
The source had witnessed an intelligence presentation made by the CIA to key US senators behind closed doors last week.
The agency's assessment, which was supposed to have been kept secret, is based on a growing body of evidence from multiple sources, the Post reports.
CIA agents allegedly say it is now "quite clear" that electing Trump was Russia's goal.
But Russian officials have denied all accusations of interference in the U.S. election.
A CIA spokeswoman said the agency had no comment on the
report.
Trump has said he is not convinced Russia was behind the
cyber attacks.
His transition team issued a statement on "claims of foreign interference in U.S. elections" on Friday but did not directly address the issue.
"These are the same people that said Saddam Hussein had weapons of mass destruction," a statement said.