Of the nearly 80 interviews with US citizens targeted by the Russian hacker group, only 2 cases were told by the FBI that they were targeted.
The intelligence agency did not immediately respond to requests for comment, but they said they "routinely inform individuals and organizations that are the target of attack."
The findings amid US government concerns that hackers working for the Russian government have penetrated US computer systems and used social media to intervene in last year's US presidential election.
Government investigators are now examining whether the Russian government has tried to influence voters and whether President Donald Trump or anyone else working near him is involved in this. During this time Trump has denied that he was involved with the Russian side.