Which security model assumes an attacker within and outside of the network and enforces strict verification before connecting to any system or resource within the organization?

The Zero Trust model is a security framework built on the principle of "never trust, always verify." It fundamentally assumes that threats can exist both inside and outside the traditional network perimeter. Consequently, it eliminates the concept of a trusted internal network. Every user, device, and application must be strictly authenticated and authorized before being granted access to any resource, regardless of its location. This continuous verification process is enforced for every access request, directly matching the scenario described in the question.

A. Biba: This is a formal security model focused on maintaining data integrity, using rules like "no read down" and "no write up," not on verifying network connections.
B. Object-capability: This model grants access based on possession of an unforgeable token (a capability), which is a specific access control mechanism, not a comprehensive network architecture.
C. Take-Grant: This is a theoretical model used to analyze the transfer of rights within a system, rather than a practical architecture for securing network access.

1. National Institute of Standards and Technology (NIST). (2020). Special Publication 800-207: Zero Trust Architecture.

Section 2.1

Tenets of Zero Trust: "A core tenet of Zero Trust is to assume that a breach is inevitable or has likely already occurred. This means the enterprise should not trust any network

device

or user by default... All resource access is done in a secure manner

and trust is not granted based on the asset or user account being on the enterprise-owned network." This directly supports the assumption of internal and external attackers and the need for strict verification.

2. Cisco. (n.d.). What Is Zero Trust?

"What Is Zero Trust?" Section

Paragraph 1: "Zero Trust is a security framework requiring all users

whether in or outside the organization’s network

to be authenticated

authorized

and continuously validated for security configuration and posture before being granted or keeping access to applications and data." This official vendor documentation confirms the core principles described in the question.

3. Bishop

M. (2005). Introduction to Computer Security. Addison-Wesley Professional.

Chapter 13

"Security Models

" pp. 360-362: This university-level textbook describes the Biba model as a formal state machine model concerned with integrity levels.

Chapter 13

"Security Models

" pp. 370-372: The Take-Grant Protection Model is explained as a formal model for analyzing the propagation of rights using a graph-based approach. These definitions clearly distinguish them from the Zero Trust architecture.