implementing-zero-trust-network-access

Implementing Zero Trust Network Access

When to Use

• When replacing traditional VPN-based remote access with identity-based access controls
• When implementing micro-segmentation to limit lateral movement within cloud networks
• When compliance or security strategy requires zero trust architecture adoption
• When providing secure access to cloud workloads without exposing them to the public internet
• When building context-aware access policies based on user identity, device health, and location

Do not use as a complete replacement for network security controls (ZTNA complements but does not replace firewalls and network ACLs), for protecting internet-facing public applications (use WAF), or for IoT device access where identity-based authentication is not feasible.

Prerequisites

• Identity provider (Entra ID, Okta, Google Workspace) with MFA enforcement
• Cloud-native networking capabilities (AWS PrivateLink, Azure Private Link, GCP IAP)
• Device management solution (Intune, Jamf, CrowdStrike) for device posture assessment
• Service mesh or zero trust proxy (Cloudflare Access, Zscaler ZPA, or cloud-native IAP)
• Centralized logging for access decisions and policy enforcement

Workflow

Step 1: Deploy GCP Identity-Aware Proxy (IAP) for Application Access

Configure IAP to provide authenticated access to web applications without VPN.

# Enable IAP API
gcloud services enable iap.googleapis.com

# Configure OAuth consent screen
gcloud iap oauth-brands create \
  --application_title="Corporate Apps" \
  --support_email=security@company.com

# Enable IAP on an App Engine application
gcloud iap web enable \
  --resource-type=app-engine \
  --oauth2-client-id=CLIENT_ID \
  --oauth2-client-secret=CLIENT_SECRET

# Enable IAP on a backend service (GCE/GKE)
gcloud compute backend-services update BACKEND_SERVICE \
  --iap=enabled,oauth2-client-id=CLIENT_ID,oauth2-client-secret=CLIENT_SECRET \
  --global

# Set IAP access policy (who can access)
gcloud iap web add-iam-policy-binding \
  --resource-type=app-engine \
  --member="group:engineering@company.com" \
  --role="roles/iap.httpsResourceAccessor"

# Configure access levels based on device and context
gcloud access-context-manager levels create corporate-device \
  --title="Corporate Managed Device" \
  --basic-level-spec=level-spec.yaml \
  --policy=POLICY_ID

Step 2: Implement AWS Verified Access for Zero Trust

Deploy AWS Verified Access to provide identity-based access to internal applications.

# Create a Verified Access trust provider (OIDC)
aws ec2 create-verified-access-trust-provider \
  --trust-provider-type user \
  --user-trust-provider-type oidc \
  --oidc-options '{
    "Issuer": "https://login.microsoftonline.com/TENANT_ID/v2.0",
    "AuthorizationEndpoint": "https://login.microsoftonline.com/TENANT_ID/oauth2/v2.0/authorize",
    "TokenEndpoint": "https://login.microsoftonline.com/TENANT_ID/oauth2/v2.0/token",
    "UserInfoEndpoint": "https://graph.microsoft.com/oidc/userinfo",
    "ClientId": "CLIENT_ID",
    "ClientSecret": "CLIENT_SECRET",
    "Scope": "openid profile email"
  }'

# Create a Verified Access instance
aws ec2 create-verified-access-instance \
  --description "Zero Trust Access Instance"

# Attach trust provider to instance
aws ec2 attach-verified-access-trust-provider \
  --verified-access-instance-id vai-INSTANCE_ID \
  --verified-access-trust-provider-id vatp-PROVIDER_ID

# Create a Verified Access group with policy
aws ec2 create-verified-access-group \
  --verified-access-instance-id vai-INSTANCE_ID \
  --policy-document '{
    "Version": "2012-10-17",
    "Statement": [{
      "Effect": "Allow",
      "Principal": "*",
      "Action": "verified-access:AllowAccess",
      "Condition": {
        "StringEquals": {
          "verified-access:user/groups": "engineering"
        }
      }
    }]
  }'

# Create endpoint for an internal application
aws ec2 create-verified-access-endpoint \
  --verified-access-group-id vag-GROUP_ID \
  --endpoint-type load-balancer \
  --attachment-type vpc \
  --domain-certificate-arn arn:aws:acm:REGION:ACCOUNT:certificate/CERT_ID \
  --application-domain app.internal.company.com \
  --endpoint-domain-prefix app \
  --load-balancer-options '{
    "LoadBalancerArn": "arn:aws:elasticloadbalancing:REGION:ACCOUNT:loadbalancer/app/internal-app/xxx",
    "Port": 443,
    "Protocol": "https",
    "SubnetIds": ["subnet-xxx"]
  }'

Step 3: Configure Azure Private Link and Conditional Access

Set up Azure Private Link for network isolation and conditional access for identity-based controls.

# Create Private Endpoint for an Azure service
az network private-endpoint create \
  --name app-private-endpoint \
  --resource-group production-rg \
  --vnet-name production-vnet \
  --subnet private-endpoint-subnet \
  --private-connection-resource-id /subscriptions/SUB_ID/resourceGroups/RG/providers/Microsoft.Web/sites/internal-app \
  --group-ids sites \
  --connection-name app-connection

# Configure private DNS zone for the service
az network private-dns zone create \
  --resource-group production-rg \
  --name privatelink.azurewebsites.net

az network private-dns link vnet create \
  --resource-group production-rg \
  --zone-name privatelink.azurewebsites.net \
  --name production-link \
  --virtual-network production-vnet \
  --registration-enabled false

# Create Conditional Access policy requiring compliant device + MFA
Connect-MgGraph -Scopes "Policy.ReadWrite.ConditionalAccess"

$params = @{
    DisplayName = "Zero Trust - Require MFA and Compliant Device"
    State = "enabled"
    Conditions = @{
        Applications = @{
            IncludeApplications = @("All")
        }
        Users = @{
            IncludeUsers = @("All")
            ExcludeGroups = @("BreakGlass-Group-ID")
        }
        Locations = @{
            IncludeLocations = @("All")
            ExcludeLocations = @("AllTrusted")
        }
    }
    GrantControls = @{
        Operator = "AND"
        BuiltInControls = @("mfa", "compliantDevice")
    }
    SessionControls = @{
        SignInFrequency = @{
            Value = 4
            Type = "hours"
            IsEnabled = $true
        }
    }
}

New-MgIdentityConditionalAccessPolicy -BodyParameter $params

Step 4: Implement Micro-Segmentation with Network Policies

Deploy network-level micro-segmentation to complement identity-based access controls.

# AWS: Create security groups for micro-segmentation
aws ec2 create-security-group \
  --group-name web-tier-sg \
  --description "Web tier - only HTTPS from ALB" \
  --vpc-id vpc-PROD

aws ec2 authorize-security-group-ingress \
  --group-id sg-WEB \
  --protocol tcp --port 443 \
  --source-group sg-ALB

aws ec2 create-security-group \
  --group-name app-tier-sg \
  --description "App tier - only from web tier"

aws ec2 authorize-security-group-ingress \
  --group-id sg-APP \
  --protocol tcp --port 8080 \
  --source-group sg-WEB

# Kubernetes NetworkPolicy for pod-level segmentation
cat << 'EOF' | kubectl apply -f -
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: api-allow-web-only
  namespace: production
spec:
  podSelector:
    matchLabels:
      app: api-server
  policyTypes:
    - Ingress
  ingress:
    - from:
        - podSelector:
            matchLabels:
              app: web-frontend
      ports:
        - protocol: TCP
          port: 8080
EOF

Step 5: Enable Continuous Verification and Logging

Implement continuous trust verification rather than one-time authentication.

# Configure CloudWatch to monitor access decisions
aws logs create-log-group --log-group-name /verified-access/access-logs

# Enable Verified Access logging
aws ec2 modify-verified-access-instance-logging-configuration \
  --verified-access-instance-id vai-INSTANCE_ID \
  --access-logs '{
    "CloudWatchLogs": {
      "Enabled": true,
      "LogGroup": "/verified-access/access-logs"
    }
  }'

# Query access logs for denied requests
aws logs start-query \
  --log-group-name /verified-access/access-logs \
  --start-time $(date -d "24 hours ago" +%s) \
  --end-time $(date +%s) \
  --query-string '
    fields @timestamp, identity.user, http_request.url, decision
    | filter decision = "deny"
    | sort @timestamp desc
    | limit 50
  '

Key Concepts

Term	Definition
Zero Trust	Security model that requires strict identity verification for every person and device accessing resources, regardless of network location
ZTNA	Zero Trust Network Access, the technology that implements zero trust principles by providing identity-aware, context-based access to applications
Identity-Aware Proxy	Proxy service that verifies user identity and device context before allowing access to backend applications, replacing VPN-based access
Micro-Segmentation	Network security technique that creates fine-grained security zones around individual workloads or applications to limit lateral movement
BeyondCorp	Google's implementation of zero trust architecture that shifts access controls from the network perimeter to individual users and devices
Continuous Verification	Ongoing assessment of user identity, device health, and access context throughout a session rather than only at authentication time

Tools & Systems

• GCP Identity-Aware Proxy: Google's BeyondCorp implementation providing context-aware access to web applications and VMs
• AWS Verified Access: AWS service for zero trust access to applications based on identity and device posture verification
• Azure Conditional Access: Microsoft's policy engine for enforcing context-based access controls based on user, device, location, and risk
• Cloudflare Access: Cloud-delivered ZTNA solution providing identity-aware access to internal applications
• Zscaler ZPA: Enterprise ZTNA platform replacing VPN with application-level access based on identity and context

Common Scenarios

Scenario: Replacing Corporate VPN with Zero Trust Access for Cloud Applications

Context: An organization with 2,000 employees accesses 30+ internal cloud applications through a traditional VPN concentrator. VPN performance issues and security concerns drive the decision to implement ZTNA.

Approach:

1. Inventory all applications currently accessed through VPN and classify by sensitivity
2. Deploy GCP IAP or AWS Verified Access for web-based internal applications
3. Configure conditional access policies requiring MFA and device compliance for all applications
4. Implement micro-segmentation using security groups to limit lateral movement between application tiers
5. Set up continuous verification with re-authentication every 4 hours for sensitive applications
6. Migrate users in phases, starting with low-risk applications, monitoring access logs for issues
7. Decommission VPN after all applications are accessible through ZTNA with full logging

Pitfalls: Not all applications support identity-aware proxy integration. Legacy thick-client applications may require agent-based ZTNA solutions instead of proxy-based approaches. Device posture assessment requires an endpoint management solution deployed to all corporate devices. Break-glass access procedures must be documented for scenarios where the identity provider is unavailable.

Output Format

Zero Trust Network Access Implementation Report
==================================================
Organization: Acme Corp
Implementation Date: 2026-02-23
Applications Migrated: 24 / 30

ZTNA ARCHITECTURE:
  Identity Provider: Microsoft Entra ID
  Access Proxy: AWS Verified Access + GCP IAP
  Device Management: Microsoft Intune
  MFA: FIDO2 + Authenticator App

ACCESS POLICY COVERAGE:
  Applications requiring MFA:          30 / 30 (100%)
  Applications requiring compliant device: 24 / 30 (80%)
  Applications with continuous verification: 18 / 30 (60%)
  Applications with location restrictions:  12 / 30 (40%)

SECURITY IMPROVEMENTS:
  VPN-related incidents (before):      12/month
  ZTNA-related incidents (after):       2/month
  Mean time to detect unauthorized access: 4 min (was 2 hours)
  Lateral movement paths eliminated:   85%

MIGRATION STATUS:
  Phase 1 (low-risk apps):     12/12 complete
  Phase 2 (medium-risk apps):  12/12 complete
  Phase 3 (high-risk apps):     0/6  in progress
  VPN decommission:            Scheduled after Phase 3