We developed our cyber defenses, largely based on variationsof a physical firewall. It does not work, and never did; it has been mathematically proven that any firewall can be penetrated.
Cyberspace is fundamentally different from physical space.

Cyberspace is an Information and Communications space.

In cyberspace information cannot be destroyed; only a copy of information can be destroyed.

Physical space is limited; cyberspace is unlimited.

Physical space has three dimensions; Cyberspace has unlimited dimensions.

In physical space visibility is unavoidable; in cyberspace visibility is optional.

In physical space only one identity is permitted; cyberspace permits multiple identities.