I'm going to answer whether the paranoia was directed at something 'real.' There was in fact widespread and pervasive Soviet infiltration of American society, especially its government, on a scale that had not been seen before and likely has not been seen since.

Documents from the Soviet's declassified archive indicate that by the 1950s hundreds--I have seen statistics range 400 to 600 hundred--of 'Americans' were working directly for the Soviet intelligence apparatus. Alger Hiss, Klaus Fuchs, the Rosenbergs, Harry Dexter White, David Salmon, Abraham Glasser, Judith Coplon, Samuel Dickstein, Lauchlin Currie and, really, the list goes on. This doesn't even begin to crack the surface of the Soviet 'attack' on the Manhattan Project or innumerable smaller episodes. On one memorable instance, the 'capture' of Office of War Information's Radio Free Italy during the later end of the war by communists within the department created a situation where the U.S. was paying for communist propaganda to be broadcast in Northern Italy.

Add in some Venona cables, the penchant for many former U.S. government employees to ride the American liberation gravy train and then detach themselves to run communist operations in Eastern Europe.

Sources; Venona: Decoding Soviet Espionage in America by John Earl Haynes, Harvey Klehr (Yale University Press); Spies: The Rise and Fall of the KGB in America by John Early Haynes (Yale University Press), How the Cold War Began by Amy Knight (Basic Books).