Zero-Trust Security Strategies for Operational Technology Environments

Digital transformation has brought a myriad of new benefits and capabilities to the operational technology (OT) world — and with it, new threats and attack vectors. Historically, OT and IT environments have operated separately. When OT environments were created, those assets were typically air-gapped from any IT resources. Over time, however, as new technologies like the Internet of Things (IoT) became involved in day-to-day operations within OT environments, those analog assets quickly went digital.

While in many cases this transformation has improved safety and brought new efficiencies to industries like manufacturing and energy, it has also unwittingly introduced more risk into OT environments. Once isolated from IT networks, OT assets are now connected to IT networks, leaving them vulnerable to cyberattacks that they were simply not designed to withstand.

The most pervasive cyber threats to OT systems include:

• The exploitation of remote access technologies
• Vulnerable ICS/OT controllers
• Adversaries accessing the ICS/OT environment through exposed assets
• Adversaries attacking the IT environment and then capitalizing on poor network segmentation, and a lack of multifactor authentication

These OT vulnerabilities can provide attackers a “way in” to the IT network, which can pose substantial risks for organizations that include breaches, reputational damage, outages of critical infrastructure and threats to human safety.

Fortunately, a zero-trust security strategy can help mitigate these risks by prioritizing strict access controls, continuous monitoring and dynamic authorization for every access request. Though many OT assets may be unable to achieve optimal zero-trust maturity, using zero-trust strategies can help manufacturers significantly reduce the risk of unauthorized access and potential data breaches.

By eliminating the assumption of trust within the network and instead requiring verification of every access request regardless of its origin, zero-trust security strategies can enhance OT security, whether those assets are built to enforce policies like least privilege access or not.

Effective zero-trust security techniques include:

• Comprehensive monitoring, which tracks all activities and provides actionable insights for quickly detecting and responding to threats.
• Dynamic access control, which continually assesses user behavior and network conditions to grant or revoke access in real time.
• Microsegmentation, which isolates parts of the environment to prevent lateral movement by attackers.

Zero-trust strategies can help OT environments enhance their resilience against cyber threats, ensuring the safety and reliability of essential operations.

Operational technology environments are unique in that they often involve critical infrastructure that must remain operational around the clock — any interruption to their operations could cost anywhere from thousands to millions of dollars in lost revenue. For this reason, OT environments have traditionally been designed to trust their legacy assets, the lifecycles of which were built to last 10-20 years in many cases.

While the traditional CIA triad security model used for guiding an organization’s data security efforts is focused on confidentiality, integrity and availability, priorities for manufacturing organizations differ slightly.

The three principles on which manufacturing security rests are:

1. Safety: Only authorized users should be able to access data or operate OT environments.

2. Throughput: Operations must always be maintained, and no party should be able to modify it either accidentally or maliciously.

3. Uptime: OT environments must be running at all required times, and authorized users must be able to access it when needed.

These three principles can help establish security priorities within OT environments. However, OT environments were designed for production, not security. It’s difficult to install even basic security guardrails like endpoint detection and response (EDR) on legacy OT assets, as they simply were not built to support them. This trust in OT assets ensures that operations stay consistently up and running but also means that many of these legacy systems are simply not compatible with modern zero-trust security measures without significant overhauls.

For example, let’s say a manufacturer attempts to segment their network by placing an OT environment on a separate LAN. This segmentation alone may change the direction of communication through a network security firewall. Now, that firewall is part of the OT environment as well. This means that if that firewall were to go down, it would impact the manufacturing line directly, leading to significant downtime and lost costs.

To avoid disruptions to production processes, non-compliance with regulations and dependencies within critical infrastructure, the first step in implementing zero-trust strategies within OT environments is to ensure that your organization has a thorough understanding of the components involved in zero-trust security.

OT security has often been underrepresented, leading to communication hurdles and uncertainties among teams about the right way forward.

Keep these six considerations in mind when structuring an OT security program:

1. Establish executive alignment: Before creating a set of controls for OT security, obtaining executive buy-in is key. The C-suite must understand the risks, rewards and necessity of OT security as the first step toward success.

2. Develop an ICS incident response plan: Since OT involves different device types and communication protocols, its incident response plan must be unique. Developing a dedicated plan with the right points of contact and specific courses of action across several scenarios is essential.

3. Invest in visibility and monitoring: One of the most important steps in successfully implementing zero-trust security strategies in OT environments, gaining visibility into all assets will help your organization discover which assets are on your network and which systems are most vulnerable. Passive monitoring to analyze systems, vulnerability maps, mitigation plans and active traffic monitoring are all key to identifying potential threats.

4. Implement risk-based vulnerability management: Once you’ve successfully discovered all assets and vulnerabilities in your OT environment, it’s time to take note of those vulnerabilities and develop a plan to manage them. An effective OT vulnerability management program should provide timely awareness of key vulnerabilities and offer alternative mitigation strategies.

5. Ensure secure remote access: Implementing multi-factor authentication (MFA) across your systems alone can help improve your OT security posture. Where MFA isn't possible, consider alternate controls like jump hosts with focused monitoring.

6. Look into microsegmentation strategies: Once extensive monitoring and secure access have been built into your OT security strategy, the next step toward optimal maturity is enforcement of zero-trust policies. Microsegmentation limits which OT assets are allowed to “communicate,” mitigating breach impacts while alerting necessary parties about attempts to access unauthorized systems. 

Engaging an expert partner with deep expertise securing both operational technology and information technology is an effective way to avoid these pitfalls and ensure that your OT environment is protected from these risks and more. As attackers become more adept at exploiting vulnerabilities and the consequences of cyber threats become more dire, zero-trust strategies can help manufacturers reduce risk while ensuring that their OT environments are secure and aligned to their organizational goals.

For those organizations who have already begun their zero-trust journeys, experts like CDW can help assess your current maturity level and provide guidance on which areas of your OT environment to target first.