The top concern for factory executives: Will security hardening affect production?
The answer is: No—provided the methodology is correct.
This article explains how to complete OT security hardening without stopping production. Our track record: zero downtime incidents caused by hardening.
What Security Threats Do OT Systems Face?
Operational Technology (OT) and Information Technology (IT) face completely different security threats:
⚠️ OT Security Threats:
- Ransomware: WannaCry caused thousands of factories worldwide to halt production
- APT Attacks: Nation-state advanced persistent threats targeting critical infrastructure
- Internal Threats: Employee errors, infected USB drives, unauthorized external connections
- Device Vulnerabilities: PLC/SCADA/HMI systems have known vulnerabilities but cannot be patched freely
- Supply Chain Attacks: Vendor remote maintenance channels exploited
The unique aspect of OT systems: Availability > Confidentiality. Production lines cannot stop, so security measures must not impact operations.
Layered Defense: Three-Tier Protection
Office Network ↔ Production Network isolation (Industrial Firewall)
Production network internal zoning (VLAN + ACL)
Critical device whitelisting (allow only known operations)
Layer 1: Boundary Isolation
Deploy an industrial firewall between office and production networks, allowing only necessary communications:
- Office network cannot directly access production network
- Only designated engineering stations can communicate across networks
- All cross-network traffic must be audited
- USB devices prohibited from cross-network use
💡 Key Point: Industrial firewalls differ from standard firewalls—they understand OT protocols (Modbus, OPC, S7, etc.) and can identify anomalous control commands.
Layer 2: Zone Segmentation
Segment the production network by function to prevent lateral attack movement:
- Production Control Zone: PLC, HMI, SCADA servers
- Monitoring Zone: Historian, MES servers
- Engineering Zone: Engineering workstations, programming devices
- Zones isolated via VLAN with ACL-controlled access
Layer 3: Device Protection
Deploy whitelisting mechanisms on critical devices (PLC, SCADA):
- Allow only known, legitimate operations
- Block execution of unknown programs
- Prohibit configuration changes (unless authorized)
- Log all operations for audit
How to Achieve "Zero-Downtime" Hardening?
Our methodology: Precise, Non-Disruptive, Zero-Interruption
- Offline Assessment (no impact on live systems)
- Network traffic mirror analysis (no device insertion)
- Vulnerability scanning (during non-production hours, on test environment)
- Configuration review (export config files for offline analysis)
- Simulation Testing (validate hardening effectiveness)
- Replicate production environment in test lab
- Verify hardening measures don't affect normal operations
- Test fault tolerance under abnormal scenarios
- Phased Implementation (edge first, core later)
- Pilot on non-critical production lines first
- After validation, roll out to critical lines
- Every change has a rollback plan
✅ Track Record: Served multiple Japanese manufacturing enterprises with zero downtime incidents from hardening. The key is the "Assess First, Test Second, Implement Third" methodology.
How to Pass MLPS Compliance?
OT systems must also pass MLPS 2.0 (Multi-Level Protection Scheme). We provide one-stop service:
- Classification & Filing: Assist in determining protection level (typically Level 3)
- Gap Analysis: Current state vs. MLPS requirements, output remediation checklist
- Hardening & Remediation: Technical measures + management policies
- Assessment Support: Assist in passing MLPS evaluation
Security Auditing: Continuous Monitoring
Security is not one-time—it requires continuous monitoring:
- Daily Monitoring: 24/7 real-time alerting
- Monthly Inspections: Vulnerability scanning, configuration audits
- Annual Audits: Comprehensive assessment, penetration testing
- Incident Response: Rapid security incident handling
About Yungu
Suzhou Yungu provides comprehensive OT security services:
- Security assessment (offline analysis, no production impact)
- Solution design (layered defense, zero-downtime hardening)
- Equipment deployment (industrial firewalls, whitelisting systems)
- MLPS compliance (classification → remediation → assessment)
- Ongoing operations (24/7 monitoring, monthly inspections)