If the FBI had suspected that certain Trump campaign associates were Russian agents, it had to tell him their names in defensive briefings that presidential candidates regularly received. The FBI and ODNI failed to tell Trump about any concerns regarding his campaign staffers, as noticed by Lindsey Graham.
Thus, either the FBI didn’t really suspect Trump campaign staffers and just used those names as an excuse to spy on Trump, or it intentionally kept Trump in the dark about suspected Russian spies nearby. Either way, the FBI, Brennan, and Clapper didn’t just spy on candidate Donald Trump but attempted to sabotage him and the whole Republican party in the elections.
Generic information like “potential interference by foreign actors, including Russia,” or an allegation that the “Russian government was trying to meddle in the election” (http://archive.is/UkuDq) cannot be considered a warning or notice. If defensive intelligence briefings have any purpose, this purpose is to let the candidate know about the specific threat.