Russian attacks on the 2016 election were detected by many sources in early 2016. The Department of Homeland Security published the proof on December 29, 2016.
On October 7, 2016, the Department Of Homeland Security (DHS) and the Office of the Director of National Intelligence (DNI) issued a joint statement on election security compromises. DHS has released a Joint Analysis Report (JAR) attributing those compromises to Russian malicious cyber activity, designated as GRIZZLY STEPPE.
The JAR package offers technical details regarding the tools and infrastructure used by Russian civilian and military intelligence services (RIS). Accompanying CSV and STIX format files of the indicators, and an enhanced analysis of GRIZZLY STEPPE activity is available:
DHS recommends that network administrators review JAR GRIZZLY-STEPPE PDF for more information and implement the recommendations provided.
EVIDENCE OF RUSSIAN INTERFERENCE IN US ELECTION: Enhanced_Analysis_of_GRIZZLY_STEPPE_ActivityPDF
"Russia is a full-scope cyber actor that poses a major threat to US government, military, diplomatic, commercial and critical infrastructure," the testimony said. It was written by James Clapper, the Director of National Intelligence, Marcel Lettre, Undersecretary of Defense for intelligence, and Admiral Michael Rogers, director of the National Security Agency.