Can couples cheat the game?

What I mean is, if you entered as a couple, be that in a relationship, mother and son, brothers, sisters or just good friends etc.

If one of you happened to be a traitor and the other faithful, could you secretly tell each other what you are in code (a certain blink or phrase said etc) could you not orchestrate with a foot in both camps you both making it to the final, one of you officially wins but you of course agree to split the money?

What could the producers even do to stop this happening?