An algo (algorithm) that is designed to ping and, then, manipulate a dark pool. It is a type of black box that attempts to game of a stock’s price, possibly by exploiting other algorithms’ flaws. A sweeper analyzes the logic behind a competitor’s algorithm by watching the way orders are placed in response to market state. When the sweeper figures out a competitor’s logic it can instantly hijack the order book to allure the target algorithm to execute its logic.

It is also known as a sniffer.