CISA issues new OT security guidance to overcome cost and complexity barriers in critical ...

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) released new guidance aimed at closing long-standing gaps in OT (operational technology) security across critical infrastructure sectors, including water and wastewater, transportation, chemical, energy, and food and agriculture. Based on interviews with OT asset owners and operators, CISA found strong demand for secure, authenticated communications but persistent barriers tied to cost, complexity, and legacy design of industrial protocols.

The guidance, titled ‘ Barriers to Secure OT Communication: Why Johnny Can’t Authenticate ,’ outlines lessons learned for operators and calls on manufacturers to reduce implementation burdens that have slowed adoption of secure-by-design communications in industrial environments. CISA conducted this research in partnership with representatives from Anybus, DNP Users Group, National Security Agency, ODVA, OPC Foundation, Rockwell Automation , Schneider Electric , The Modbus Organization, and Xylem.

This guidance aims to provide a clearer path for owners and operators seeking to implement secure communications safely, as well as for OT manufacturers, including industrial automation and control system vendors, suppliers, and OEMs (original equipment manufacturers), working to improve usability by removing the cost and complexity barriers facing their customers. It builds on secure communication principles outlined in earlier Secure by Design OT publications, further advancing practical adoption across industrial environments.

To understand how to help the OT community shift away from legacy industrial protocols to more secure technology, CISA and partners, including OT manufacturers and protocol standard development organizations, conducted voice of customer (VoC) research focused on asset owners and operators of varying maturity across critical infrastructure sectors.

The research used individual and group interviews to identify how asset owners understand secure communication in OT, and what barriers organizations encounter on the user journey across procurement , design, deployment, and operations. It recognizes that parts of OT networks will inevitably use legacy protocols until organizations replace them with newer components. However, operators will only use the secure protocol in new components if the technology is usable by operators in an OT environment. Secure communication in OT is a long-term effort, requiring collaboration between asset owners and operators, system integrators, service providers, and OT manufacturers.

Legacy OT protocols lack strong protections against data alteration, device impersonation, and unauthorized access, making critical infrastructure vulnerable to cyber threats. Securing these protocols requires solutions that are practical for current operators and cyber experts. Based on the research conducted, CISA provides recommendations for how owners and operators can avoid the negative experiences of their peers, as well as recommendations to OT manufacturers to drive sustainable, more usable capabilities.

CISA’s research found confusion among operators what ‘secure communication’ actually requires, particularly the distinction between signing and encryption. The guidance defines signing as providing integrity and authentication, and encryption as providing confidentiality, stressing that signing should be prioritized and can be implemented without encryption, while encryption often includes signing but must be properly validated. It also distinguishes between encrypting operational data, which can introduce latency and limit inspection, and encrypting network management functions, which is essential to protect credentials and keys.

Operators are primarily motivated to adopt secure communications to ensure the integrity and authenticity of OT data and prevent threats such as actor-in-the-middle attacks, unauthorized commands, and malicious firmware updates. Encryption is typically pursued to securely push updates, aggregate field data, and prevent adversaries from inspecting compromised networks. However, adoption is hindered by cost and availability concerns, particularly around performance impacts and the complexity of implementing and managing technologies such as PKI (public key infrastructure) across the system lifecycle.

Through the VoC research, CISA found that, in their pursuit of secure communications, operators encountered barriers from initial conception and procurement , through deployment and operations. The two main barriers were cost and availability concerns stemming from data encryption. The agency examined the source of secure communication costs throughout a system’s lifecycle and how the location of secure communication changed perceptions around availability concerns. Additionally, it looked into the role of PKI and how operators currently interface with it.

CISA found that many organizations delayed or declined to implement secure communications because of significant upfront and ongoing costs, including retrofitting legacy systems, upgrading hardware for cryptography, managing certificates, licensing fees, training staff, and maintaining compliance.

During procurement, operators often faced a choice between fully upgrading components to support secure protocols, which can cost as much as the original equipment and carry licensing fees, or ‘wrapping’ legacy traffic with gateways that add authentication but provide less comprehensive protection. Given these costs and uncertainty long-term protocol stability, many chose segmentation and continuous monitoring as more predictable investments, while expressing concern crypto longevity and vendor lock-in.

Even after procurement, deployment, and maintenance posed challenges, particularly the complexity and expense of implementing and managing PKI, which often required third-party support. Operators weighed these burdens against other security priorities and frequently found segmentation or bolt-on tools easier to justify. While secure communications can enable micro-segmentation and reduce spoofing and integrity risks, adoption remains limited unless solutions simplify workflows, support crypto-agility, and are strategically applied to high-risk areas such as remote access , boundary communications, and firmware updates.

Manufacturers can address cost barriers by building systems with crypto-agility to remove the fear of buying at the wrong time. They can be transparent security infrastructure costs, include secure communication capabilities by default, reduce complexity to lower costs, and track key performance indicators (KPIs) related to the usability of security features. They can maximize opportunities to move away from legacy communication patterns by defaulting to secure configurations, guiding users through the required security infrastructure, such as public key infrastructure, and preconfiguring integrated systems to use secure communications as a built-in form of micro-segmentation.

CISA found that operators are reluctant to adopt secure communications if they believe it could disrupt normal engineering or business operations, especially given past negative experiences with security tools. Concerns fall into three areas: reduced observability if traffic is encrypted and harder to inspect, potential latency and bandwidth constraints on legacy infrastructure, and uncertainty how secure communications will function in practice. While newer systems can mitigate performance issues and selective encryption can preserve visibility, many operators remain cautious, particularly in brownfield environments.

Confidence gaps also influence how and where secure communications are deployed, with security teams often prioritizing northbound traffic and field operators showing greater risk aversion. Questions around handling expired or invalid certificates further complicate adoption, especially for safety-critical messages. CISA advises organizations to phase in secure communications gradually, beginning with signing and logging before moving to enforcement measures such as dropping unauthenticated packets as trust in the infrastructure grows.

Manufacturers can reduce availability concerns by adopting open standards and participating in interoperability testing and certification wherever possible, increasing confidence that secure communications will not disrupt operations. They should also publish testing results that outline minimum network bandwidth requirements when secure communications are used with common products, and provide clear, practical upgrade paths for legacy infrastructure.

Nearly all operators cited difficulties deploying and maintaining public key infrastructure, describing it as complex during both setup and ongoing operations, and raising concerns added connectivity risks. Initial certificate provisioning often requires specialized expertise and third-party support, particularly for configuring certificate managers and distributing keys, though newer protocol versions offer more automation. CISA noted that few interviewees mentioned alternatives such as pre-shared keys, suggesting limited awareness of other options and a need for clearer vendor communication.

Operationally, responsibility for PKI can fall into a gray area between OT teams managing field devices and security teams overseeing network infrastructure, leaving some operators handling key management without sufficient experience. While management software can automate key rotation and enable more granular segmentation, some organizations worry that centralized certificate authorities could weaken network segmentation by requiring broader connectivity. Balancing manageability with connectivity risk remains a key challenge.

While this research does not directly address post-quantum cryptography (PQC), the CISA document recognizes it as important to briefly it as a looming problem for secure communications adoption. PQC adoption in OT suffers from the same general adoption problems highlighted in this guidance. If technology is difficult to use, costly, or prone to causing downtime, then it is unlikely to be adopted. PQC raises the importance of crypto-agility, as it is likely that the PQC transition will need to occur during the lifespan of any products purchased in the 2020s.

The industry will also need to pay close attention to key exchange mechanisms, as the larger keyspace will significantly increase network utilization during key exchange. Network utilization affecting system availability is already a concern, but this is likely to exacerbate the limitations of older network infrastructure and endpoints, putting more pressure on integrators and manufacturers to simplify the initial key deployment.

CISA called upon owners and operators to implement signing across all OT communications and apply encryption where necessary to protect sensitive data such as passwords, key exchanges, and logic updates. If there are concerns reduced visibility or downtime caused by key management issues, they should consider a phased rollout that begins with signing only and logging, rather than immediately dropping unauthenticated packets.

They should prioritize products that support crypto-agility so cryptographic algorithms can be updated over the product’s lifespan, and look for vendor solutions that simplify secure workflows through management tools, guided configuration, and system integrator support. Organizations should also ensure that open standard protocol implementations are properly certified, including their security features, such as key exchange mechanisms.

Secure communications should be prioritized for remote access paths, communications across functional or network boundaries, and firmware uploads or logic changes to reduce exposure and limit the impact of malicious actors. Finally, operators should select products that streamline initial key provisioning and work with experienced integrators to deploy security infrastructure such as PKI, while adopting secure discovery and provisioning capabilities that allow certificate managers to onboard new components.

In conclusion, CISA noted that despite being available for decades, secure versions of industrial protocols remain underused across OT environments. CISA’s 2025 Secure by Demand for OT guidance underscores the urgent need to implement secure communications, using signing and, where appropriate, encryption, to defend against threats such as actor-in-the-middle attacks and unauthorized firmware or configuration changes. Asset owners are motivated by ensuring the integrity and authenticity of OT communications. However, widespread adoption of secure communications is hindered not by a lack of technical solutions but by real-world barriers in cost, complexity, and operational risk.

“Cost is driven by high procurement costs and licensing fees for secure-capable components and then exacerbated by complex solutions driving operators towards external assistance to deploy and maintain secure infrastructure,” according to the agency. “Complexity is increased for operators by poor integrator contracts, proprietary protocols, and unclear manufacturer guidance. Operational risk is driven by concerns over visibility, legacy infrastructure limitations, and interoperability issues. This research shows that operators desire the benefits of secure communication. Manufacturers and integrators need to factor in the usability of security to make that operator desire a reality.”