President Obama is asking for the review to be complete before he leaves office on January 20th. There will be a review of the last three presidential elections.
The concern is “malicious cyber activity” in which Russia was explicitly named. This does not mean election results will change.
Trump, so far, has not hit Twitter on this matter.
“U.S. intelligence officials have said they believe Russia actively attempted to interfere with the U.S. presidential election, including a hack of the Democratic National Committee’s email system.”