A second Red Scare.
A red scare is the promotion of fear of rise of communism or radical leftism, used by anti-leftist proponents. Alger Hiss was part of the Second Red Scare, where the terror was focused on national and foreign communists influencing society and/or infiltrating the federal government. The Rosenbergs were tried for espionnage during the same Second Red Scare. This has also been called "McCarthyism" after the Senator, who was it's most famous supporter. Both red scares are best defined as internal communist fear.