Muddy Waters Research LLC is an American privately held due diligence based investment firm that conducts investigative research on public companies while also taking investment positions that reflect their research. The firm has exposed accounting problems and fraud at several companies, primarily in China but also in other countries in Asia, Europe and North America. The firm is best known for spotting fraud at Sino-Forest Corp, a Canadian-listed Chinese company whose stock fell 74 percent before it eventually filed for bankruptcy protection in March 2012.