OT security at the highest level thanks to open-source alternatives: Commercial OT security solutions such as those from Nozomi Networks, Darktrace, Forescout or Microsoft Defender for IoT promise a wide range of functions, but are often associated with license costs in the mid to high six-figure range per year. Such a high investment is often difficult to justify internally, especially in economically difficult times.In contrast, open source tools offer some decisive advantages:
Lower costs: no license fees, only investment in hardware and implementation.Flexibility and adaptability: Source code is freely available and can be adapted to specific requirements in the OT environment.Active community: Continuous further development and rapid response to new threats.However, open source solutions usually require a well-positioned IT/OT security team to implement, configure and operate these tools correctly. Support also tends to be “community-driven” or provided by specialized service providers. Nevertheless, practice shows that professional planning enables a level of security that can keep up with that of expensive providers in many respects. Recommended open source tool combinations for maximum coverage: In order to cover as many security functions as possible, a combination of several open source tools is recommended. These can be expanded on a modular basis, which enables better adaptation to the respective OT landscape. Here are some examples:
Asset management and network transparency
- Malcolm (incl. Zeek)
Focus: Real-time network analysis and specialized OT protocol support.Advantages:
Deep packet inspection, comprehensive protocol analysis (including Modbus and DNP3)Continuous asset discovery through passive monitoringSpecially designed for ICS/SCADA environmentsSupplement: GRASSMARLIN for network visualizationGraphically displays topologies in industrial environmentsHelps to identify unknown network paths and segmentation problems2. NetboxFocus: IP address management and comprehensive OT asset documentation.Advantages:
Centralized inventory and “single source of truth” for network infrastructuresSimple integration into CMDB processesEssential basis for further security measures such as segmentation, network access controls.
Network monitoring and anomaly detection
- Security Onion (Suricata Zeek)
Focus: Real-time threat detection, network forensics.Benefits:
Provides IDS/IPS functionalities (Suricata or Snort) and log analysis (Zeek) in a comprehensive packageIntegrated dashboards (e.g. Kibana) for alerting and analysisEasily scalable from small test setups to large production sites2. ELK stack (Elasticsearch, Logstash, Kibana)Focus: Central logging and visualization platform.Advantages:
Powerful search and analysis options for log dataLong-term analysis and correlation of events from different sourcesFlexible dashboards for security managers
Vulnerability management and endpoint security
- Wazuh
Focus: XDR (extended detection and response), compliance and vulnerability management.Advantages:
Central monitoring of end devices (HMIs, SCADA servers, operator stations, etc.)File integrity monitoring and active detection of security incidentsCompliance support (e.g. TISAX, ITAR, PCI-DSS)2. OpenVAS (Greenbone Vulnerability Manager)Focus: Active vulnerability scans to identify potential gaps.Advantages:
Regularly updated database with known vulnerabilitiesSupplements passive monitoring with active scan functionsCovers a broad spectrum of systems
Incident response and security operations
- TheHive & Cortex
Focus: Incident management, case management, workflow automation.Advantages:
Fast and structured processing of security incidentsIntegration of predefined or own IR playbooksAnalysis modules (Cortex) enable automatic queries of IoCs or threat feeds2. OpenCTIFocus: Threat intelligence management, integration of external feeds.Advantages:
Central collection, correlation and analysis of threat informationSupport for proactive defense measuresPerfect addition to security data from Security Onion, Wazuh & Co. Further additions for a comprehensive OT security concept:
ICS-specific honeypots (e.g. Conpot): Serve as an “early warning system” and provide insights into attack strategies before the real production systems are affected.OT-specific machine learning projects: Those who want more AI functionality can rely on PyTorch, TensorFlow or specialized research projects. However, this often requires extensive data science expertise.Rule and signature packs: To adapt Suricata/Zeek even better to industrial protocols, ICS-specific rules (e.g. via emerging threats, industrial control systems signatures) can be integrated. Opportunities and limitations of open source: With the open source tools described above, a wide range of functions can be realized that comes surprisingly close to that of commercial solutions. The strengths lie in cost efficiency, flexibility and community support. At the same time, you should bear the following in mind:
No automatic “plug & play”: unlike commercial solutions, you have to invest time in installation, configuration and fine-tuning.Machine learning functionalities are available (especially with Suricata, Zeek and supplementary ML frameworks), but often require more know-how than the out-of-the-box solutions from high-priced providers.Support and maintenance: Instead of dedicated manufacturer support, a combination of community forums, documentation and, if necessary, individual service providers is usually relied upon.Nevertheless, practical experience shows that with a competent OT security team or external consultants, open source solutions can also be used successfully on a large scale.
First seen on csoonline.com
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