Stephen Brunauer was a civilian employee of the U.S. Navy, working as a chemist in the explosive research division. Brunauer had been in the Young Communist League in the late 1920s but appears to have abandoned the movement by the early 1940s and in 1946 the U.S. government sent him to Hungary (he was Hungarian born) to assist in the escape of Hungarian scientists from Communist Hungary. There were also cases were some association legitimately raised security risk concerns but on inspection, the association appears to have been coincidental. 
Senator Joseph McCarthy stated, "Brunauer, an admitted former member of the Young Communist League, was suspended from his job as head of the Navy's high explosives section where he was engaged in top secret work. He resigned before the Navy's Loyalty Board could complete questioning him and dispose of his case." Brunauer also had a reputation for associating with know Communists. McCarthy stated, "For example, his very good friend, Noel Field, a known Communist and espionage agent, spent night after night with Stephen Brunauer, who had access to all the top secrets in the explosive section of our Navy. Field then left the country, and has since disappeared behind the iron curtain, taking with him all the information which his friend Brunauer had given him ... What forced the Navy to take action was that it appeared during the atom-spy investigations that Stephen Brunauer was involved." 
A memorandum in the Silvermaster file from FBI Director J. Edgar Hoover to Admiral Inglis of the Office of Naval Intelligence (ONI) dated 1947 informs ONI Stephan Brunauer had been investigated under the Atomic Energy Act upon request of the Atomic Energy Commission (AEC) in March of 1947 and upon receipt of the completed results from the FBI & Navy of the investigation by the AEC Brunauer had been denied access to restricted data under the Atomic Energy Act.
Hoover further advised that if the investigation of Brunauer had been continued it would have involved a violation of the Delimitation Agreement in that Brunauer was a civilian. The investigation and its conclusions were conducted prior to a new Executive order on Loyalty of Government Employees and the FBI understood the Department of the Navy was also conducting its own investigation of Brunauer. 
- Senator Joseph McCarthy’s Lists and Venona, by John Earl Haynes, April 2007.
- Buckley, Jr., William F. and Bozell, L. Brent (1954, 1995 Printing). McCarthy & His Enemies, The Record And It's Meaning. Regnery Publishing Inc.. ISBN 0-89526-472-2. McCarthy, Joseph (1953). Major Speeches and Debates of Senator Joe McCarthy Delivered in the United States Senate, 1950-1951. U. S. Government Printing Office. ISBN 0-87968-308-2. Congressional Record, (May 8, 1951). Page 5058. U. S. Government Printing Office. )
- FBI Silvermaster file Vol. 134 November—December 1947, pgs. 66-67.