The first step is a commercially available computer system that does not have built-in security gaps.  WinTel machines are not secure and cannot be made secure.  Apple is the same.  Unix is hopeless.  Linux is better but can still be penetrated.  As part of this, any digital device should have factory installed first level security.  The most common password for mobile devices is "passwd."  Even a random 8 byte password is better than that.

She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre