## Identity as the Perimeter

The new firewall is the Login Screen.

### Authentication vs Authorization
*   **AuthN**: Who are you? (MFA).
*   **AuthZ**: What can you do? (Roles).

### The Signal
Zero Trust creates a "Risk Signal" based on context:
*   **User**: Is Bob.
*   **Device**: Corporate Laptop (Managed).
*   **Location**: Office IP.
*   **Behavior**: Normal hours.
*   **Result**: Allow Access.

*   **Change**: Bob logs in from an unmanaged iPad in Russia.
*   **Result**: Block (even if password is correct).