evidence points conclusively to north korea and north korea alone hasn't changed even after the fbi health the courtesy meeting that they had with private cyber scientists who dispute that claim. >> reporter: despite skepticism among some cyber experts, the fbi is standing firm by its conclusion that the north korean government is responsible for the devastating sony hack. a conclusion reinforced by president obama. >> i think it was an act of cyber vandalism that was very costly very expensive. we will respond proportionately. >> reporter: some cyber scientists argue the u.s. government has it all wrong saying that the sony hack was an inside job. the silicon valley based firm presented their case to fbi agents in a three-hour meeting monday night. evidence they say points to four suspects including at least one former employee. a woman code named leena who