What is Least Privilege?
Least Privilege is a fundamental security principle whereby a user, device or process is granted only the minimum rights required to perform its task — no more and no less.
In OT networks, applying Least Privilege prevents unauthorised actions or access to critical systems, whether deliberate or accidental.
🧠 How does Least Privilege work?
- Each user, service or component receives exactly the access rights required for specific functions
- Access to system functions, network segments or devices is restricted via RBAC, ACL, and Group Policy
- Permissions are regularly reviewed and revoked when they are no longer needed
- Restrictions apply to:
- User accounts
- Applications
- Network traffic
- Remote access
Least Privilege is a pillar of the Zero Trust model and Defense in Depth.
🏭 Applying Least Privilege in OT networks
- Only engineers may make changes to PLCs or SCADA
- Operators receive access only to their process zone or workstation
- Service accounts for maintenance receive temporary, limited access
- Access to network segments is restricted via Firewall and VLAN
- Remote Access (e.g. via Jump Server) is protected with per-user access and time restrictions
Applying Least Privilege reduces the risk of sabotage, misuse or mistakes within OT environments.
🔍 Least Privilege vs. Admin by Default
| Aspect | Least Privilege | Default administration (insecure) |
|---|---|---|
| Access rights | Only what is required | Everything open or admin rights |
| Risk of misuse | Greatly reduced | High |
| Management | Fine-grained, controlled | Quick but insecure |
| Use in OT | Recommended – improves availability and safety | Still common in legacy installations |
🔐 Security considerations
- Combine with RBAC or ABAC (Attribute-Based Access Control)
- Implement via Active Directory or Entra ID with Group Policy
- Reduce the attack surface for Malware, Phishing or insider threats
- Monitor and log all permission changes via SIEM
- Automate revocation of rights when roles change or upon offboarding
A user with too many rights is a potential security risk, even without malicious intent.
📌 In summary
Least Privilege is a fundamental principle for limiting access to what is truly needed, and is therefore essential for secure OT networks. By minimising and managing permissions, the likelihood of errors, attacks or sabotage is drastically reduced.