FBI director James Comey said that the tool used by the bureau to unlock the phone belonging to one of the San Bernardino shooters only works 'on a narrow slice of phones', and it will not be efficient on newer models of iPhones (like 5s, 6 and 6s). The director also mentioned that the government has purchased the tool from a private party, and that he is confident that the respective party 'is very good at protection it'.