Zero Trust Security Implementation Checklist for IT Teams

# Zero Trust Security Implementation Checklist for IT Teams

Zero Trust operates on a single principle: never trust, always verify. Unlike perimeter-based security, Zero Trust assumes breach and enforces least-privilege access at every layer. This checklist walks your IT team through each implementation phase with concrete, actionable steps.

Phase 1: Assess Your Current State

Before implementing Zero Trust, map what you have.

1.1 Identity Inventory

• List all user accounts (employees, contractors, service accounts)
• Identify privileged accounts and admin roles
• Audit accounts with standing access vs. just-in-time access
• Document all identity providers (Active Directory, Okta, Azure AD, etc.)
• Flag dormant accounts inactive for 30+ days

1.2 Device Inventory

• Enumerate all managed endpoints (laptops, desktops, mobile)
• Identify unmanaged/BYOD devices accessing corporate resources
• Document device compliance status (OS version, patch level, encryption)
• List IoT and OT devices on the network

1.3 Application & Data Inventory

• Catalogue all SaaS, on-prem, and cloud-hosted applications
• Classify data by sensitivity (public, internal, confidential, restricted)
• Map which users/roles access which applications
• Identify applications with no SSO integration

Phase 2: Identity & Access Management

Identity is the new perimeter in Zero Trust.

2.1 Multi-Factor Authentication (MFA)

2.2 Single Sign-On (SSO)

• Integrate all critical applications with your SSO provider
• Enforce SSO - disable direct login where possible
• Review and remove unused OAuth app authorisations quarterly
• Enable SSO session timeout policies (e.g., re-authenticate after 8 hours)

2.3 Least Privilege Access

• Audit all role assignments - remove excess permissions
• Implement Role-Based Access Control (RBAC) for all applications
• Replace standing privileged access with just-in-time (JIT) elevation
• Review and certify access rights every 90 days
• Disable shared/generic accounts; assign individual identities

2.4 Conditional Access Policies

Define access rules based on context:

Phase 3: Device Security & Compliance

3.1 Endpoint Management

• Enrol all corporate devices in MDM/UEM (Intune, Jamf, etc.)
• Define and enforce device compliance policies:

• •OS must be within 1 major version of current
• •Disk encryption enabled (BitLocker / FileVault)
• •Antivirus/EDR agent installed and active
• •Screen lock after 5 minutes of inactivity
• •[ ] Block non-compliant devices from accessing corporate resources
• •[ ] Enable remote wipe capability for all managed devices

3.2 Endpoint Detection & Response (EDR)

• Deploy EDR on all managed endpoints
• Configure alerts for suspicious process execution, lateral movement
• Integrate EDR telemetry with your SIEM
• Define and test incident response runbooks for common EDR alerts

Phase 4: Network Segmentation & Access

4.1 Micro-Segmentation

• Map current network topology and traffic flows
• Segment the network by function (e.g., corporate, guest, IoT, servers)
• Apply firewall rules to restrict east-west traffic between segments
• Deny all traffic by default; allow only explicitly defined flows
• Review firewall rules quarterly and remove stale rules

4.2 Replace VPN with Zero Trust Network Access (ZTNA)

4.3 DNS Security

• Deploy DNS filtering (e.g., Cloudflare Gateway, Cisco Umbrella)
• Block known malicious domains and C2 infrastructure
• Enable DNS-over-HTTPS (DoH) or DNS-over-TLS (DoT) for all endpoints
• Log all DNS queries for threat hunting

Phase 5: Data Protection

• Enable Data Loss Prevention (DLP) policies on email and file sharing
• Classify and label sensitive documents (Microsoft Purview, Google DLP)
• Restrict copy/paste and download of sensitive data to unmanaged devices
• Encrypt sensitive data at rest and in transit
• Audit external sharing settings in Google Workspace / Microsoft 365
• Define and enforce data retention and deletion policies

Phase 6: Monitoring & Continuous Verification

Zero Trust is not a one-time project - it requires ongoing verification.

6.1 Logging & SIEM

• Centralise logs from identity, endpoints, network, and applications
• Define alert rules for high-risk events (impossible travel, mass downloads, etc.)
• Set log retention to meet compliance requirements (minimum 90 days hot, 1 year cold)
• Assign ownership for alert triage and response

6.2 Regular Reviews

Quick-Reference: Zero Trust Maturity Levels

Next Steps

1. 1Score your current state against each phase above
2. 2Prioritise gaps by risk (identity and MFA first)
3. 3Build a 90-day roadmap with owners and milestones
4. 4Review progress monthly and adjust

Zero Trust is a journey, not a destination. Start with the highest-impact controls and iterate.