Zero Trust

Definition

Zero Trust is a security framework that assumes no user, device, or network traffic should be trusted by default — whether inside or outside the network perimeter. Every access request is verified, authenticated, and authorized before granting access.

Zero Trust is summarized by the principle: “Never trust, always verify.” It was popularized by Forrester (2010) and later adopted by NIST (SP 800-207) and the US government.

Zero Trust vs Traditional Security

Aspect Traditional (Perimeter-based) Zero Trust
Trust model Trust inside, distrust outside No implicit trust, anywhere
Network boundary Firewall perimeter No fixed boundary (cloud, remote)
Access control Network-based (IP ranges) Identity-based (user/device context)
Lateral movement Limited by network segmentation Micro-segmentation prevents it
Breach assumption Assume perimeter holds Assume breach is inevitable
Example Corporate VPN + firewall SASE, ZTNA, identity-aware proxies

Zero Trust Principles (NIST SP 800-207)

  1. All data sources and services are resources
  2. Access is established before connection (verify identity first)
  3. Access is granted as least privilege (minimum required)
  4. Access decisions are dynamic (context-aware: time, location, device health)
  5. Assume breach (minimize blast radius, verify explicitly)

Zero Trust Architecture (NIST)

Policy Engine
    │
    ├── Identity & Access Management (IAM)
    ├── Device Health Verification
    ├── Context (time, location, risk score)
    └── Authorization (least privilege)
            │
            ▼
    Trust Decision (allow/deny/require MFA)
            │
            ▼
    Enforcement Point (proxy, SDP, firewall)
            │
            ▼
    Resource (app, database, service)

Zero Trust Components

Component Purpose
Identity Provider (IdP) Verify user identity (OAuth, SAML, OIDC)
MFA (Multi-Factor Auth) Require multiple verification factors
Device Posture Check Verify device is compliant (patched, encrypted)
Micro-segmentation Segment network to limit lateral movement
SDP (Software-Defined Perimeter) Hide services until authenticated
ZTNA (Zero Trust Network Access) Replace VPN with application-level access
SIEM/SOAR Monitor and respond to threats
PAM (Privileged Access Mgmt) Control and monitor privileged access

Zero Trust vs VPN

Feature VPN ZTNA
Access scope Network-level (entire subnet) Application-level (specific apps)
Trust model Trust after VPN connection Verify every request
Lateral movement Possible after VPN Prevented by app-level access
User experience Connect to network, then browse Direct app access, no network login
Security Weaker (broad access) Stronger (least privilege)
Example Cisco AnyConnect, OpenVPN Zscaler, Cloudflare Access, Netskope

Zero Trust Implementation Steps

  1. Inventory assets — identify all resources, users, devices
  2. Map traffic flows — understand how data moves
  3. Architect Zero Trust — define policies, identity, segmentation
  4. Monitor and control — implement ZTNA, SIEM, MFA
  5. Automate and integrate — connect components, automate responses
  6. Educate users — training on new access patterns

Zero Trust Tools

Tool Type Vendor
Zscaler Internet Access ZTNA/SASE Zscaler
Cloudflare Access ZTNA Cloudflare
Netskope SASE/ZTNA Netskope
Cisco Secure ZTNA Cisco
BeyondCorp ZTNA Google
OPA Policy enforcement CNCF
Istio Service mesh (micro-segmentation) CNCF
  • mTLS — mutual TLS for device/service authentication
  • IAM — identity is the perimeter in Zero Trust
  • MFA — multi-factor auth is core to Zero Trust
  • SDP — software-defined perimeter for Zero Trust
  • Waf — monitoring and threat detection

References