Introduction
Traditional network security was based on the perimeter defense model, protecting the enterprise network “boundary” with firewalls and VPNs. However, cloud adoption, remote work expansion, and BYOD have blurred the line between the trusted “inside” and untrusted “outside.”
Zero Trust Architecture (ZTA) is a security model based on the principle “Never trust, always verify.”
History of Zero Trust
| Year | Event |
|---|---|
| 2010 | John Kindervag at Forrester Research coined “Zero Trust” |
| 2014 | Google published BeyondCorp papers (eliminating VPN for internal access) |
| 2020 | NIST published SP 800-207 “Zero Trust Architecture” |
| 2021 | US Executive Order 14028 mandated Zero Trust for federal agencies |
Core Principles (NIST SP 800-207)
NIST SP 800-207 defines seven core principles:
All data sources and computing services are considered resources
- Personal devices accessing enterprise resources are managed as resources
All communication is secured regardless of network location
- Internal LAN traffic is encrypted and authenticated
Access to individual resources is granted on a per-session basis
- No persistent access from a single authentication
Access is determined by dynamic policy
- User ID, device state, location, time, behavioral patterns are holistically evaluated
Integrity and security posture of all assets are monitored and measured
- Unpatched or misconfigured devices receive lower trust scores
Authentication and authorization are strictly enforced before access
- Multi-factor authentication (MFA) and least privilege principle
Collected data is continuously used to improve security posture
- Log analysis, anomaly detection, and policy optimization cycles
Key Components
Logical Architecture
User/Device
↓
[Policy Enforcement Point (PEP)] ← Access control point
↓
[Policy Administrator (PA)] ← Establishes/terminates connections
↓
[Policy Engine (PE)] ← Access decision brain
↑
┌─────────────────┐
│ Data Sources │
│ · Identity Provider (IdP) │
│ · SIEM / Log Analysis │
│ · Threat Intelligence │
│ · Device Management (MDM) │
│ · Compliance DB │
└─────────────────┘
| Component | Role |
|---|---|
| Policy Engine (PE) | Makes access decisions based on context |
| Policy Administrator (PA) | Establishes/terminates sessions per PE decisions |
| Policy Enforcement Point (PEP) | Gateway that enforces actual access control |
| Identity Provider (IdP) | User authentication and attribute provision |
| SIEM | Security event collection and correlation analysis |
| MDM/EDR | Device health and security posture assessment |
Comparison with Perimeter Defense
| Aspect | Perimeter Defense | Zero Trust |
|---|---|---|
| Trust basis | Network location | Verified identity + context |
| Internal network treatment | Implicitly trusted | Never trusted, always verified |
| Access control | Network-level | Resource-level |
| VPN requirement | Essential | Unnecessary (per-application access) |
| Lateral movement defense | Limited | Suppressed via micro-segmentation |
| Visibility | Boundary traffic only | All communications visible |
| Remote work support | VPN-dependent | Same policy regardless of location |
Implementation Approaches
Identity-Centric
Strengthen identity management and MFA for trust-based access control.
- Universal SSO + MFA deployment
- Contextual authentication (device, location, time, risk score)
- Just-in-Time (JIT) access
Network-Centric
Use micro-segmentation to divide networks finely and prevent lateral movement.
- VLAN / firewall rule granularization
- Software-Defined Networking (SDN)
- East-west traffic inspection
Software-Defined Perimeter (SDP)
Control access at the application level, hiding the network itself. Resources are invisible until authentication succeeds.
Phased Implementation Plan
| Phase | Measures | Goal |
|---|---|---|
| Phase 1 | Identity foundation | Deploy MFA for all users, SSO integration, identity governance |
| Phase 2 | Device trust establishment | Deploy MDM/EDR, device health checks, compliance verification |
| Phase 3 | Micro-segmentation | Network segmentation, per-application access control |
| Phase 4 | Continuous monitoring | SIEM integration, anomaly detection, automated policy adjustment |
Implementation Challenges
Legacy System Integration
Older systems may not support modern authentication protocols (OAuth 2.0, SAML). Proxy or adapter layers may be needed.
User Experience Impact
Increased authentication frequency may reduce convenience. Balance with risk-based authentication and passkeys.
Cost and Complexity
Phased deployment is recommended, starting with high-ROI areas (privileged access management, critical data protection).
Related Articles
- CISSP: Comparison of Key Security Governance Frameworks - Understand Zero Trust’s position within the broader security framework landscape.
- Comparison of Major Security Models - Relationship between access control models like Bell-LaPadula and Zero Trust.
- Email Authentication Mechanisms (SPF, DKIM, DMARC) - Email authentication as part of Zero Trust.
- Comparison and Guide to Information Security Certifications - Certification paths related to Zero Trust.
- Micro Hardening Training Report - Hands-on security training experience.
References
- Rose, S., Borchert, O., Mitchell, S., & Connelly, S. (2020). NIST SP 800-207: Zero Trust Architecture. National Institute of Standards and Technology.
- Ward, R., & Beyer, B. (2014). “BeyondCorp: A New Approach to Enterprise Security”. ;login:, 39(6).
- Executive Order 14028 (2021). “Improving the Nation’s Cybersecurity”.