In my current game as England/emperor/epic/fractal/large I can't block any other civs from stealing tech, even though I have spy in London, constabulary, police station, and the Order policy that doubles chance of capturing spies. I haven't caught a single foreign spy the entire game (I'm in modern era now), in spite of having max spy defense at all times. Is this intentional? All but 3 other civs were wiped out by the barbs, but I liberated all their cities to reduce places for camps to spawn and wipes out all barb cities. Now I'm just doing wack-a-mole when new camps spawn, but the inability to stop other civs from stealing all my tech is frustrating.