What is Zero Trust?
Zero Trust is a cybersecurity model based on the principle:
“Trust nothing, verify everything.”
In contrast to traditional security models — which automatically trust traffic inside the network — Zero Trust holds that no user, device or connection is ever trusted by default, not even within the ‘internal’ environment.
🎯 The aim of Zero Trust
- Prevent lateral movement by attackers within a network
- Grant minimum access rights (least privilege)
- Use identity, context and behaviour as the basis for access
- Better resilience against insider threats, Ransomware and supply chain attacks
- Meet modern compliance requirements such as NIS2, ISO 27001 and BIO
🔐 Core principles of Zero Trust
| Principle | Explanation |
|---|---|
| Verify explicitly | Continuously authenticate and authorise, based on multiple factors (MFA) |
| Least privilege access | Users and systems only get access to what is strictly necessary |
| Assume breach | Assume attackers are already inside and limit their spread |
| Microsegmentation | Divide the network into small, logically separated zones |
| Continuous monitoring | Real-time logging, behaviour and anomaly detection |
🛠️ Components of a Zero Trust architecture
| Component | Description |
|---|---|
| Identity management | MFA, RBAC, IAM systems such as Azure AD or Okta |
| Device management | EDR, MDM, Asset Management |
| Network segmentation | VLAN, SDN, zones and conduits model in line with IEC 62443 |
| Access control | VPN, ZTNA, PAM and Firewall policy at session level |
| Monitoring & detection | SIEM, UEBA, XDR, SOC |
🏭 Zero Trust in OT/industrial networks
In OT, Zero Trust is challenging but achievable with the right adaptations:
- Segmentation per production line, cell or protocol
- Authentication of remote engineers or contractors
- Allowing only specific protocol traffic (e.g. Modbus read-only)
- Control of HMI/SCADA access via Jump Server
- Integration of Firewall, IDS/IPS and Asset Inventory
✅ Benefits of Zero Trust
- Limits the impact of attacks, even when an attacker is ‘inside’
- Protects hybrid environments (cloud, on-premises, OT, remote)
- Supports compliance and audit traceability
- Reduces dependence on classical network perimeters
- Improves visibility and control across all layers
⚠️ Challenges in implementation
- Legacy systems that do not support modern authentication
- OT devices without endpoint agents
- Cultural change: ‘trust’ is no longer the default
- Complexity of integrations and management
- The starting point requires a phased approach with clear priorities
📌 In summary
Zero Trust is a modern security model based on the principle of ‘never trust, always verify’. It protects organisations against complex threats by placing identity, behaviour and context at the heart of access decisions.