IIRC such a group as SIGMA played a major role in Niven and Pounelle’s Footfall. Advising the POTUS and JCS as to how to respond to an alien attack.
You could extend the rumor further to include a certain percentage of illegals that are getting deported, have disappeared, instead being diverted to donor camps where the organs are harvested.
I know that SDI was basically cooked up in Niven’s livin g room, and Pournelle was one of the people there.