SENATOR INFORMED OF ALLEGED ASSASSINATION PLOT IN EARLY SEPTEMBER

Senator Dianne Feinstein claims that she was informed of the alleged Iranian plot to kill the Saudi Ambassador to the USA in early September.

Feinstein said she was initially skeptical when she was first briefed about the alleged plot in early September but now believed "it's very real."

[source : Lawmakers say alleged Iran plot was "very real", Reuters, 16/10/2011, http://www.reuters.com/article/2011/10/16/us-usa-iran-congress-idUSTRE79F1NW20111016

What exactly was she told, and by whom?