Michael but could also easily be someone like Miles. Ben would never let someone off the island so I can see him pointing Michael in the direction of the "enemy" freighter only to be "rescued" by them. He then turns the tables and has Michael spy for him. But I could also see Miles being the inside man. Michael still ended up on the freighter in the same way, he just doesn't have any connection to Ben anymore. I think either one of the two guys could be working for Ben.