We propose a mathematical procedure for finding informed traders in ultra-high frequency trading. We wrote it as Vector ARMA and found condition of its stationarity. For the price exposure complied with ARMA(1,2) we proved that underlying asset price difference can be derived as ARMA(1,1) process. For validation of the model, we test an influence of informed traders in EUR/USD, GBP/USD, USD/RUB pairs and futures, in gold and futures prices, in Russian Trade System share index (RTS) and futures t...