US-listed Netflix has adopted a poison pill defense to prevent a hostile takeover, acting just days after activist investor Carl Icahn disclosed he had bought a stake in the streaming video and DVD-by-mail subscription service. The move is meant to prevent an outsider who lacks Netflix board approval from accumulating a stake of 10 per cent or more, the company said in a statement yesterday. The measure, approved by the board on Friday, remains in effect for three years. Last Wednesday, Icahn disclosed that he had amassed control of 9.98 per cent of Netflix shares. Most of his purchases were in the form of call options that expire in September 2014. The billionaire is known for shaking up management.