From the September 14 edition of CNN's The Lead with Jake Tapper:
DREW GRIFFIN: It's called the Internet Research Agency. A company U.S. intelligence officials called “Russia's Troll Army”, a state funded organization that blogs and tweets on behalf of the Kremlin. Facebook is one of the top sites Russians target to spread their fake messages and that is why congressional investigators are demanding Facebook open up its own records, help track the fake Russian news, find out who was behind it.
The fake sites, the fake stories, were mostly negative about Hillary Clinton and either supported or promoted far right positions that were being pushed by Donald Trump. Experts say the overall effect was to spread so much disinformation, it all just started to look real, and attacks on the so-called mainstream media played right into the Russians' hands.