Some articles on sayanim:

Clandestine HUMINT Operational Techniques - Staff and Skills in A Clandestine HUMINT Operations Station - Support Services - Volunteer and Proprietary Support
... Sayanim are Jews living outside Israel as foreign citizens that volunteer to provide assistance to the Mossad ... money, logistics, and even overt intelligence gathering, yet sayanim are only paid for their expenses ... No official number is known, but estimates put the number of sayanim in the thousands ...