 The view of communism was also affected by evidence of espionage in the US conducted by agents of the USSR . In 1945 , a Soviet spy , Elizabeth Bentley , repudiated the USSR and provided a list of Soviet spies in the US to the Federal Bureau of Investigation ( FBI ) . The FBI also had access to secret Soviet communications , available from the Venona decryption effort , which revealed significant efforts by Soviet agents to conduct espionage within the US . The growing influence of communism around the world and the evidence of Soviet spies within the US motivated the Department of Justice – spearheaded by the FBI – to initiate an investigation of communists within the US . 
