The cybersecurity industry has always had a fortress mentality: Firewall the perimeter! Harden the system! But that mindset has failed—miserably, as each new headline-generating hack reminds us. Even if you do patch all your software, the way Equifax didn’t, or you randomize all your passwords, the way most of us don’t, bad actors are going to get past your heavily guarded gate, into your network. And once they do, they’re free to go wild.