Securing Your OT Network

1. Network Segmentation: Isolate the OT network from the broader corporate network and the internet. Implement network segmentation to create separate zones for different OT systems and control access between them with “default-deny” firewall rules.
2. Access Control: Enforce strict access controls to limit who can access and make changes to the OT network. Use strong authentication methods, like multi-factor authentication (MFA), and follow the principle of least privilege. Don’t re-use logins for OT equipment.
3. Patch and Update Management: Regularly update and patch all software and firmware in the OT network, including industrial control systems (ICS) components and network equipment. Be cautious when applying updates and thoroughly test them in a controlled environment prior to rolling them out to a production environment.
4. Network Monitoring: Implement continuous monitoring to detect abnormal network behavior or security incidents. Use intrusion detection and prevention systems (IDPS) and security information and event management (SIEM) solutions to analyze network traffic and log data.
5. Air-Gap Critical Systems: For the most critical OT systems, consider physically isolating them from the network by creating a true air gap. While this may not always be practical, it provides an additional layer of security. This is especially important for legacy equipment that does not get regular security updates.
6. Security Policies and Procedures: Develop and enforce comprehensive security policies and procedures specific to the OT environment. These should cover topics like incident response, remote access, and configuration management.
7. Application Whitelisting: Use application whitelisting to allow only authorized software and applications to run on OT devices and systems. This prevents the execution of unapproved software.
8. Physical Security: Secure physical access to critical OT infrastructure, such as control rooms and industrial equipment. Install security cameras, access control systems, and alarms to monitor and control entry.
9. Regular Backups: Implement regular backups of critical data and configurations to ensure rapid recovery in case of a cyber incident or system failure. Backups should be monitored, encrypted in transit and at rest, and have an offsite copy to protect from ransomware.
10. Incident Response Plan: Develop a well-documented incident response plan specific to OT networks. The plan should outline the steps to be taken in case of a security breach and should be tested periodically. Other incidents to include would be extended power outages and any local relevant natural disasters that could hit your area.
11. Vendor and Supply Chain Security: Evaluate the security practices of OT equipment and software vendors. Ensure that your supply chain is secure, and that vendors provide timely security updates. Require vendors working on site to use your own managed computers for accessing the systems instead of plugging in directly with their own devices. Require vendors to provide cyber security policies for their own operations.
12. Regulatory Compliance: Understand and comply with relevant industry standards and regulations specific to your sector, such as NIST, ISA/IEC 62443, or other applicable guidelines.
13. Security Assessment and Audits: Regularly engage in security assessments and audits to evaluate the effectiveness of your OT security measures and identify areas for improvement.

Securing an OT network is an ongoing process that requires continuous monitoring, assessment, and adaptation to evolving threats. The specific security measures you implement will depend on the unique characteristics and requirements of your OT environment. Collaboration between IT and OT teams is essential to ensure a holistic and effective security strategy.