The Informant!

The U.S. government decides to go after an agri-business big corporation with a price-fixing accusation, based on the evidence submitted by their star witness, vice president turned informant Mark Whitacre (Matt Damon). A rising star at agri-industry giant Archer Daniels Midland (ADM), Whitacre suddenly turns whistleblower. Even as he exposes his company's multi-national price-fixing conspiracy to the FBI, Whitacre envisions himself being hailed as a hero of the common man and handed a promotion. But before all that can happen, the FBI needs evidence, so Whitacre eagerly agrees to wear a wire and carry a hidden tape recorder in his briefcase, imagining himself as a kind of de facto secret agent.