Spies normally need to search for individuals out there, to incite them against their country and divulge secrets. However, at times, a prospective asset just appears at the door of the embassy. These are called, “volunteers,” or “walk-ins” even though it is not necessary for them to practically be present in an area.
Aldrich Ames, an ex CIA Officer and Robert Hanssen, an ex FBI agent were both Soviet KGB’s “volunteers. ”