“Never trust, always verify” sounds great in a slide deck. But how do you actually implement Zero Trust in a real system? This guide breaks it down.

Photo by Markus Spiske on Unsplash

What Zero Trust Actually Means

Traditional security: “Everything inside the network is trusted.”

Zero Trust: “Nothing is trusted. Every request must prove its legitimacy.”

The perimeter is dead. Your users work from coffee shops. Your services run across multiple clouds. Your “internal network” is a myth.

The Five Pillars of Zero Trust

1. Identity Verification

Every request needs a verified identity—human or machine.

# Example: OAuth2 + JWT validation in API Gateway
apiVersion: networking.istio.io/v1beta1
kind: RequestAuthentication
metadata:
  name: jwt-auth
spec:
  jwtRules:
    - issuer: "https://auth.example.com"
      jwksUri: "https://auth.example.com/.well-known/jwks.json"
      audiences:
        - "api.example.com"

Key practices:

• Multi-factor authentication (MFA) everywhere
• Short-lived tokens (< 1 hour)
• Service-to-service authentication (mTLS, SPIFFE)

2. Device Trust

The identity isn’t enough—is the device secure?

# Device posture check before granting access
def check_device_posture(device_info):
    checks = [
        device_info.os_version >= MIN_OS_VERSION,
        device_info.disk_encrypted,
        device_info.firewall_enabled,
        device_info.antivirus_updated,
        device_info.not_jailbroken,
    ]
    return all(checks)

Tools:

• Google BeyondCorp Enterprise
• Microsoft Conditional Access
• Kolide (for Slack-based checks)

3. Network Segmentation

Microsegmentation limits blast radius:

# Kubernetes NetworkPolicy - only allow specific traffic
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: api-policy
  namespace: production
spec:
  podSelector:
    matchLabels:
      app: api
  policyTypes:
    - Ingress
    - Egress
  ingress:
    - from:
        - podSelector:
            matchLabels:
              app: gateway
      ports:
        - port: 8080
  egress:
    - to:
        - podSelector:
            matchLabels:
              app: database
      ports:
        - port: 5432

Photo by Jordan Harrison on Unsplash

4. Least Privilege Access

Grant minimum permissions needed, for minimum time:

# Terraform: Time-bound IAM role
resource "aws_iam_role" "developer_access" {
  name               = "developer-temp-access"
  max_session_duration = 3600  # 1 hour max

  assume_role_policy = jsonencode({
    Version = "2012-10-17"
    Statement = [{
      Effect = "Allow"
      Principal = {
        Federated = "arn:aws:iam::123456789:saml-provider/Okta"
      }
      Action = "sts:AssumeRoleWithSAML"
      Condition = {
        StringEquals = {
          "SAML:aud" = "https://signin.aws.amazon.com/saml"
        }
      }
    }]
  })
}

Implement:

• Just-in-time (JIT) access
• Role-based access control (RBAC)
• Attribute-based access control (ABAC)

5. Continuous Monitoring

Trust is verified continuously, not just at login:

# Anomaly detection for API access
class AccessMonitor:
    def check_request(self, request, user_context):
        risk_score = 0
        
        # Geographic anomaly
        if request.location != user_context.usual_location:
            risk_score += 30
        
        # Time anomaly
        if not user_context.is_working_hours(request.time):
            risk_score += 20
        
        # Behavioral anomaly
        if request.action not in user_context.common_actions:
            risk_score += 25
        
        # Device anomaly
        if request.device_id not in user_context.known_devices:
            risk_score += 40
        
        if risk_score > 50:
            return self.require_step_up_auth()
        
        return self.allow()

Implementation Roadmap

Phase 1: Foundation (Months 1-3)

• Implement SSO with MFA
• Inventory all identities (human + service)
• Enable logging everywhere
• Map data flows

Phase 2: Segmentation (Months 4-6)

• Network policies in Kubernetes
• Service mesh (Istio/Linkerd) with mTLS
• Database access controls
• Secrets management (Vault)

Phase 3: Continuous Verification (Months 7-9)

• Device posture checks
• Behavioral analytics
• Automated response to anomalies
• Regular access reviews

Phase 4: Optimization (Months 10-12)

• Risk-based authentication
• Policy as code
• Chaos engineering for security
• Red team exercises

Service Mesh: The Zero Trust Backbone

Istio provides Zero Trust networking out of the box:

# Enforce mTLS for all services
apiVersion: security.istio.io/v1beta1
kind: PeerAuthentication
metadata:
  name: default
  namespace: istio-system
spec:
  mtls:
    mode: STRICT

---
# Authorization policy
apiVersion: security.istio.io/v1beta1
kind: AuthorizationPolicy
metadata:
  name: api-authz
spec:
  selector:
    matchLabels:
      app: api
  rules:
    - from:
        - source:
            principals: ["cluster.local/ns/prod/sa/gateway"]
      to:
        - operation:
            methods: ["GET", "POST"]
            paths: ["/api/v1/*"]

Common Mistakes

Measuring Success

Track these metrics:

• MTTD (Mean Time to Detect): How fast you spot threats
• Lateral movement attempts: Should decrease
• Access request denials: Should be low (good UX)
• Privileged access duration: Should decrease over time

Tools Ecosystem

Conclusion

Zero Trust isn’t a product you buy—it’s an architecture you build. Start with identity, add layers incrementally, and never stop verifying.

The goal isn’t to eliminate trust. It’s to make trust explicit, verified, and minimal.

Further reading: NIST Zero Trust Architecture (SP 800-207)

이 글이 도움이 되셨다면 공감 및 광고 클릭을 부탁드립니다 :)