I do not know if it is right to pose here. I am quite confused how famous hedge funds, like DE SHAW and Jame Simons protect their trading secrecy? If they trade via other brokers, the brokers can peer into their trading strategies; if they do not trade via brokers, it means they have to build broker services for themselves and clearing for themselves too, which is a lot of work. In case they become their own brokers, how can they short stocks since they can not borrow shares from other clients? Given that Jame simons does not employ too many people, how can they maintain a brokerage for themselves? thanks for any input here.