Stealing it's basically getting infiltrate in the roulette (the spy icon). If you get infiltrate you have to choose between 3 options. All of them have money but the one they tell you to find it's the one with the highest amount. There's nothing you can do to avoid other players to steal from you, but now you lose only a fraction of your total of money. On release date was almost unplayable since they stole ALL your money.