From USA Today:

Q&A: Why the CIA, FBI differ on Russian election hacking


Q: Is there suspicion that Russian hackers may have tampered with votes?

A: No. Federal officials, including Homeland Security Secretary Jeh Johnson and FBI Director James Comey, have said that the decentralized nature of voting systems across the U.S. poses a difficult target for hackers.

"In our judgment, it would be very difficult to alter a ballot count in any one place and have a significant consequence,'' Johnson said in an interview last month with USA TODAY.