Regulators manage conflicts of interest within banking conglomerates by enforcing China Walls—internal information barriers around dealers—and to evaluate their effectiveness, this study maps information sharing between dealers and funds using Israeli Shekel foreign exchange trades, comparing trading activities of affiliates against unrelated firms around exceptionally large trades to detect information sharing. The research documents islands of informational autarky between dealers and their affiliate funds surrounded by a sea of information sharing, finding that dealers never trade nor share information with their affiliated funds, dealers consistently share information with their client funds including on non-trading days, and affiliated funds intensely share information among themselves since they are free to do so. Back-of-the-envelope calculations suggest that establishing China Walls between affiliated funds would eliminate $16.1 billion in trades, comprising 37% of their trades on event dates, with these results holding during both crisis and noncrisis periods across granular cells of firm and asset characteristics, ultimately revealing remarkable regulatory capacity to control information flows within financial conglomerates.