What is an iDMZ?
An iDMZ (Industrial Demilitarized Zone) is a secured network zone that acts as a buffer between the office IT network and the production OT network. The iDMZ prevents direct communication between IT and OT, and controls and restricts data flows between the two worlds.
The iDMZ is an essential component of a Defense in Depth architecture in industrial networks.
🧠 How does an iDMZ work?
- The iDMZ is an intermediary network environment shielded by two firewalls:
- One firewall between IT and the iDMZ
- One firewall between OT and the iDMZ
- Only controlled and defined data flows are permitted, via:
- Proxies
- Jump Servers
- Remote desktop RDP
- Historians
- Secure file transfer
- iDMZs support unidirectional communication, often via data diodes or appropriate filtering
This means OT systems are protected from malware, attacks and unintended IT influence.
🏭 Application of iDMZ in industrial networks
- Placement of a Historian in the iDMZ for data exchange with ERP/MES
- Use of a Jump Server to manage OT systems from IT workstations
- Central location for Antivirus updates or patch management towards OT
- External suppliers log on to iDMZ servers, not directly to OT equipment
- SIEM connectors or Syslog forwarding from OT → iDMZ → IT/SOC
A correctly configured iDMZ prevents lateral movement of attackers between IT and OT.
🔍 Difference between DMZ and iDMZ
| Aspect | DMZ (classic) | iDMZ (industrial application) |
|---|---|---|
| Purpose | Separating public services from the internal network | Separating IT and OT networks |
| Location | Between the internet and the internal network | Between the IT network and the OT network |
| Examples | Web server, mail server | Historian, jump server, SIEM collector |
| Security | Rule-based, often less specific | Very strict, with deep packet inspection and logging |
🔐 Security aspects
- The iDMZ prevents direct connections between OT ↔ IT → reducing the risk of ransomware spreading
- Combine with Firewall, network segmentation, Access Control, MFA
- Only essential protocols (e.g. HTTPS, OPC UA, Syslog) are allowed
- Monitoring via anomaly detection or SIEM is essential for logging and forensics
- Supports IEC 62443, Zero Trust and NIS2 requirements
Many attacks in OT begin via IT → iDMZ → OT – segmentation is crucial.
📌 In summary
An iDMZ is a critical security zone that enables secure data exchange between IT and OT without direct linkage. It protects production environments from cyber risks originating in the office environment and from external access.