Zero Trust operates on the principle 'never trust, always verify,' replacing perimeter-based security with identity-centric controls and least-privilege access. Every access request is authenticated, authorized, and encrypted before granting minimal necessary permissions, with continuous monitoring for anomalies. Google implemented a zero trust model called BeyondCorp, allowing employees to work securely from any location without a VPN by verifying device health and user identity for each application access. This approach is particularly effective against insider threats, compromised credentials, and attacks that bypass traditional perimeter defenses.