Zero Trust Framework

14 min read

Updated Jun 18, 2025

Introduction

Zero Trust is a security model that requires all users, whether inside or outside the organization's network, to be authenticated, authorized, and continuously validated before being granted access to applications and data.

Key Concept: "Never trust, always verify" - Zero Trust eliminates the concept of a trusted internal network and untrusted external network.

Traditional vs Zero Trust Security

Traditional Perimeter Security:
┌─────────────────────────────────────────┐
│          Trusted Internal Network        │
│  ┌─────┐  ┌─────┐  ┌─────┐  ┌─────┐   │
│  │User │  │User │  │Apps │  │Data │   │
│  └─────┘  └─────┘  └─────┘  └─────┘   │
│                                         │
│            🔐 Firewall 🔐               │
└─────────────────────────────────────────┘
                    │
        Untrusted External Network

Zero Trust Architecture:
┌─────────────────────────────────────────┐
│         Everything is Untrusted         │
│  ┌─────┐  ┌─────┐  ┌─────┐  ┌─────┐   │
│  │User │──┤Verify├──┤Apps │──┤Data │   │
│  └─────┘  └─────┘  └─────┘  └─────┘   │
│     │         │         │        │      │
│     └─────────┴─────────┴────────┘      │
│          Continuous Verification        │
└─────────────────────────────────────────┘

Core Principles of Zero Trust

Zero Trust is built on fundamental principles that guide its implementation:

Verify Explicitly

Always authenticate and authorize based on all available data points including user identity, location, device health, service or workload, data classification, and anomalies.

Least Privilege Access

Limit user access with just-in-time and just-enough-access (JIT/JEA), risk-based adaptive policies, and data protection to minimize exposure.

Assume Breach

Minimize blast radius and segment access. Verify end-to-end encryption and use analytics to get visibility, drive threat detection, and improve defenses.

Zero Trust Architecture Overview

A comprehensive Zero Trust architecture encompasses multiple layers of security controls:

┌─────────────────────────────────────────────────────────┐
│                   Zero Trust Architecture                │
├─────────────────────────────────────────────────────────┤
│                                                         │
│  ┌─────────────┐    ┌─────────────┐    ┌────────────┐ │
│  │   Identity   │    │   Devices   │    │    Data    │ │
│  │  & Access   │    │   & Trust   │    │ Protection │ │
│  └──────┬──────┘    └──────┬──────┘    └─────┬──────┘ │
│         │                  │                  │        │
│         └──────────────────┴──────────────────┘        │
│                           │                            │
│                    ┌──────▼──────┐                    │
│                    │Policy Engine│                    │
│                    │  & Decision │                    │
│                    └──────┬──────┘                    │
│                           │                            │
│         ┌─────────────────┴─────────────────┐         │
│         │                                   │         │
│  ┌──────▼──────┐  ┌──────▼──────┐  ┌──────▼──────┐  │
│  │  Network     │  │ Application │  │ Analytics & │  │
│  │ Segmentation│  │   Gateway   │  │ Monitoring  │  │
│  └─────────────┘  └─────────────┘  └─────────────┘  │
│                                                       │
└───────────────────────────────────────────────────────┘

Key Components

Policy Decision Point (PDP) - Central brain for access decisions
Policy Enforcement Point (PEP) - Enforces access decisions
Policy Information Point (PIP) - Provides context for decisions
Policy Administration Point (PAP) - Policy management interface

Identity and Access Management

Identity is the foundation of Zero Trust. Every access decision starts with strong identity verification.

Multi-Factor Authentication (MFA)

# Example MFA policy configuration
{
  "mfa_policy": {
    "name": "zero_trust_mfa",
    "rules": [
      {
        "condition": "all_users",
        "requirements": {
          "factors": ["password", "phone|hardware_token"],
          "remember_device": false,
          "session_lifetime": "8h"
        }
      },
      {
        "condition": "privileged_access",
        "requirements": {
          "factors": ["password", "hardware_token", "biometric"],
          "remember_device": false,
          "session_lifetime": "1h",
          "reauthentication": "sensitive_operations"
        }
      }
    ]
  }
}

Privileged Access Management (PAM)

Just-In-Time (JIT) access provisioning
Privilege elevation workflows with approval
Session recording and monitoring
Automated de-provisioning
Regular access reviews and certification

Best Practice: Implement passwordless authentication where possible using FIDO2, Windows Hello, or biometric methods.

Network Security

Zero Trust networks use micro-segmentation and encryption to protect data flows.

Micro-Segmentation Strategy

# Network segmentation rules example
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: zero-trust-web-policy
spec:
  podSelector:
    matchLabels:
      app: web-frontend
  policyTypes:
  - Ingress
  - Egress
  ingress:
  - from:
    - namespaceSelector:
        matchLabels:
          name: load-balancer
    ports:
    - protocol: TCP
      port: 8080
  egress:
  - to:
    - podSelector:
        matchLabels:
          app: api-backend
    ports:
    - protocol: TCP
      port: 3000
  - to:
    - namespaceSelector:
        matchLabels:
          name: monitoring
    ports:
    - protocol: TCP
      port: 9090

Software-Defined Perimeter (SDP)

Dynamic secure connectivity based on identity
Application-layer encryption for all communications
Context-aware access controls
Reduced attack surface through cloaking

Device Trust and Compliance

Every device must be verified and compliant before accessing resources.

Device Health Checks

{
  "device_compliance_policy": {
    "windows": {
      "os_version": ">=10.0.19041",
      "antivirus": {
        "enabled": true,
        "up_to_date": true,
        "real_time_protection": true
      },
      "firewall": "enabled",
      "disk_encryption": "bitlocker_enabled",
      "patches": {
        "critical": "installed_within_7_days",
        "important": "installed_within_14_days"
      }
    },
    "mac": {
      "os_version": ">=11.0",
      "firewall": "enabled",
      "disk_encryption": "filevault_enabled",
      "system_integrity_protection": "enabled"
    },
    "mobile": {
      "jailbreak_detection": true,
      "app_protection_policies": "enabled",
      "pin_required": true,
      "biometric_enabled": true
    }
  }
}

Certificate-Based Authentication

PKI infrastructure for device certificates
Mutual TLS for all connections
Certificate lifecycle management
Hardware-backed key storage (TPM/Secure Enclave)

Application Security

Applications must be secured at multiple layers in a Zero Trust model.

Application Proxy and Gateway

# Zero Trust Application Gateway configuration
server {
    listen 443 ssl http2;
    server_name app.example.com;
    
    # Mutual TLS
    ssl_client_certificate /etc/nginx/ca.crt;
    ssl_verify_client on;
    
    # Security headers
    add_header X-Frame-Options "DENY" always;
    add_header X-Content-Type-Options "nosniff" always;
    add_header X-XSS-Protection "1; mode=block" always;
    add_header Content-Security-Policy "default-src 'self'" always;
    
    location / {
        # Verify JWT token
        auth_request /auth;
        auth_request_set $auth_status $upstream_status;
        
        # Add user context headers
        proxy_set_header X-User-ID $jwt_claim_sub;
        proxy_set_header X-User-Groups $jwt_claim_groups;
        proxy_set_header X-Device-Trust $device_trust_level;
        
        # Proxy to backend
        proxy_pass http://backend;
    }
    
    location = /auth {
        internal;
        proxy_pass http://auth-service/verify;
        proxy_set_header Content-Length "";
        proxy_pass_request_body off;
    }
}

API Security

OAuth 2.0 / OpenID Connect for API authentication
Rate limiting and throttling per identity
API versioning and deprecation policies
Request/response validation and sanitization
API activity monitoring and analytics

Data Protection

Data must be protected at rest, in transit, and in use.

Data Classification and Labeling

{
  "data_classification": {
    "levels": [
      {
        "name": "public",
        "color": "green",
        "encryption": "optional",
        "access": "all_users"
      },
      {
        "name": "internal",
        "color": "yellow",
        "encryption": "required_at_rest",
        "access": "employees_only"
      },
      {
        "name": "confidential",
        "color": "orange",
        "encryption": "required_always",
        "access": "need_to_know",
        "dlp_rules": "enabled"
      },
      {
        "name": "restricted",
        "color": "red",
        "encryption": "hardware_security_module",
        "access": "explicit_approval",
        "dlp_rules": "strict",
        "audit": "all_access"
      }
    ]
  }
}

Encryption Strategy

TLS 1.3 minimum for data in transit
AES-256 encryption for data at rest
Key management with HSM integration
Encrypted databases with field-level encryption
Secure key rotation procedures

Implementation Roadmap

Implementing Zero Trust is a journey. Here's a phased approach:

Phase 1: Foundation (Months 1-3)

Establish core identity and access management capabilities.

Deploy MFA for all users
Implement SSO across applications
Create identity governance processes
Establish baseline security policies

Phase 2: Device Trust (Months 4-6)

Implement device compliance and management.

Deploy endpoint protection platform
Implement device compliance policies
Enable conditional access based on device health
Roll out certificate-based authentication

Phase 3: Network Segmentation (Months 7-9)

Implement micro-segmentation and secure connectivity.

Deploy software-defined perimeter
Implement network micro-segmentation
Enable encrypted tunnels for all communications
Remove legacy VPN dependencies

Phase 4: Application Security (Months 10-12)

Secure applications and APIs with Zero Trust principles.

Deploy application proxy/gateway
Implement API security controls
Enable application-layer encryption
Integrate with SIEM/SOAR platforms

Monitoring and Analytics

Continuous monitoring is essential for Zero Trust effectiveness.

Key Metrics to Monitor

# Prometheus metrics for Zero Trust monitoring
# Authentication metrics
auth_attempts_total{result="success|failure", method="password|mfa|certificate"}
auth_anomalies_detected{type="location|time|device|behavior"}
session_duration_seconds{user_type="standard|privileged"}

# Device compliance metrics
device_compliance_status{status="compliant|non_compliant", os="windows|mac|linux"}
device_health_score{device_id="...", score="0-100"}
certificate_expiry_days{device_id="...", days_remaining="..."}

# Access metrics
access_requests_total{resource="...", result="granted|denied", reason="..."}
privilege_escalations_total{user="...", role="...", approved="true|false"}
policy_violations_total{policy="...", severity="low|medium|high|critical"}

# Network metrics
connection_attempts_total{source="...", destination="...", result="allowed|blocked"}
data_transfer_bytes{classification="public|internal|confidential|restricted"}
encryption_coverage_percent{type="at_rest|in_transit"}

Security Analytics and UEBA

User and Entity Behavior Analytics (UEBA)
Anomaly detection with machine learning
Risk scoring for adaptive authentication
Automated threat response workflows
Compliance reporting and dashboards

Technology Stack

Okta/Azure AD

Identity Provider

CrowdStrike/Tanium

Endpoint Security

Zscaler/Prisma

SASE Platform

Splunk/Elastic

SIEM/Analytics

HashiCorp Vault

Secrets Management

Open Policy Agent

Policy Engine

Success Tip: Start with high-value assets and expand gradually. Zero Trust is not a product but a strategy that requires continuous improvement.