They were named in the VENONA documents, I believe.
Game, set, match, guilty.
Venonoa nailed them for the traitors they were, and Martin Sobol, their attorney, friend, and arch defender said recently that he and Jules were both spies in the service of stalin and his workers’ paradise.....
http://www.latimes.com/news/opinion/la-oe-radosh17-2008sep17,0,490961.story