Securing Syslog Transfer from OT to IT

Syslogs are essential for monitoring and forensic visibility across Operational Technology (OT) environments. Devices like PLCs, RTUs, and industrial controllers generate syslogs to inform OT SIEMs and upstream IT teams about process anomalies, system status, and operational insights.

However, in many industrial networks, these syslogs are sent over insecure, bidirectional channels, often exposing the OT layer to external threats. What appears to be harmless monitoring data can become a gateway for sophisticated cyber attacks targeting critical infrastructure.

Several high-profile attacks demonstrate the critical security risks associated with unsecured syslog channels and monitoring interfaces.

Industroyer 2 attack in Ukraine during 2022 saw attackers manipulate grid control systems via open monitoring ports used for log exports, leading to planned blackouts. The attackers specifically targeted diagnostic interfaces that were meant for operational visibility.

The Triton Malware incident in the Middle East in 2017 gained access through a safety system's diagnostics interface and log channel, nearly causing catastrophic explosions. The malware specifically targeted safety instrumented systems through monitoring pathways that were considered secure.

The Florida Water Hack in Oldsmar in 2021 showed how attackers gained access through exposed remote interfaces used for log viewing and diagnostics. The incident highlighted how seemingly innocuous monitoring access can lead to direct control system manipulation.

These cases prove a critical reality that any return path from IT to OT, even for logging, can be lethal to industrial operations and public safety.

Syslog traffic seems innocent, but when exposed through firewalls or VPNs, it can open a command and control route into your industrial equipment. The bidirectional nature of traditional syslog implementations creates multiple attack vectors that can be exploited by sophisticated threat actors.

Attackers can exploit these channels to inject false logs, misleading operators about actual system conditions and creating confusion during critical operations. They can tamper with alerting thresholds, modifying alarm conditions to hide malicious activities or cause false alarms that overwhelm operational staff.

More dangerously, attackers can trigger false positives or suppress real alerts, manipulating the monitoring system to either overwhelm operators with meaningless alarms or hide genuine threats. They can also use the connection as a pivot point, leveraging the syslog channel to reach deeper OT assets and establish persistent access throughout the industrial network.

The fundamental problem is that traditional syslog implementations create a two-way communication channel where only one-way data flow is actually needed for operational visibility.

The Terafence Unidirectional Secure Gateway solves this problem with FPGA-based data diode technology, enforcing one-way-only transmission from OT to IT. This hardware-enforced approach provides absolute security guarantees that software solutions cannot match.

The system eliminates all inbound IP traffic, completely removing the possibility of remote exploits through the syslog channel. Unlike software-based security solutions, this hardware-enforced air gap is not dependent on software firewalls or configuration settings that can be compromised or misconfigured.

The gateway supports standard syslog protocols over UDP and TCP without requiring any modifications to existing infrastructure. It is specifically designed for compatibility with PLCs, RTUs, ICS and SCADA devices commonly found in industrial networks.

A real-world implementation in a power utility demonstrates the effectiveness of this approach. Terafence enabled secure transmission of syslogs from Siemens S7 PLCs and ABB RTUs to an IT SIEM, without exposing the control network to external threats. The implementation maintained full operational visibility while achieving true network segmentation.

With Terafence's unidirectional security gateway, organizations achieve comprehensive protection without sacrificing operational visibility. The solution provides a physical-layer air gap between OT and IT environments, creating hardware-enforced separation that cannot be bypassed through software vulnerabilities or misconfigurations.

The architecture creates zero attack surface into the OT environment by completely eliminating return pathways that attackers could exploit to access industrial control systems. This approach ensures tamper-proof logging and analytics, maintaining the integrity of operational data while preventing any possibility of log manipulation or injection attacks.

Organizations implementing this solution achieve compliance with strict requirements from CERT-In guidelines, NERC CIP standards, and other critical infrastructure security frameworks. The implementation provides complete audit trails and verifiable security controls that meet the most demanding regulatory requirements.

The result is a security architecture where organizations don't just monitor their OT environment, they protect it with absolute certainty. This represents true IT-OT segmentation that maintains operational efficiency while providing uncompromising security.