Complete Guide to Third-Party Vendor and OEM Access for OT/ICS
Third-party vendors and OEMs play a critical role in the operation and maintenance of industrial control systems (ICS) and operational technology (OT). From equipment manufacturers and integrators to remote support teams, external users often require direct access to critical systems for diagnostics, updates, and service delivery. In most OT environments, third-party access is not an edge case. It is how systems stay operational.
This access is necessary, but it also introduces risk. Most third-party connections originate from unmanaged devices, traverse unsecured networks, and operate outside the organization’s direct control. As a result, third-party access is now one of the most targeted and least governed threat vectors in OT environments.
This guide provides a comprehensive overview of how third-party and OEM access works in OT and ICS, why it presents unique challenges, and what controls are required to manage it securely.
Key Takeaways
- Third-party access is common in OT and ICS environments for support, maintenance, and integration.
- External users often require direct access to sensitive systems and applications.
- Most third-party access involves unmanaged endpoints and untrusted networks.
- Poorly governed third-party access introduces serious security and compliance risks.
What is third-party vendor and OEM access in OT and ICS?
Third-party access in OT, ICS, and cyber physical systems (CPS) environments refers to the ability for external users such as equipment manufacturers, system integrators, contractors, or service providers to remotely connect to industrial systems. These users typically perform tasks such as diagnostics, firmware updates, routine maintenance, remote support, or emergency troubleshooting.
This access is often temporary, task-specific, and high-privilege. Unlike internal users, third-party users are not part of the organization’s identity infrastructure, and their access commonly originates from unmanaged or external devices. Despite this, they frequently require interaction with highly sensitive control systems such as PLCs, HMIs, SCADA servers, historian databases, or networked field equipment.
Third-party and OEM access is distinct from internal access in three critical ways: it originates outside the trusted network, it typically bypasses enterprise identity governance, and it often lacks consistent policy enforcement. In OT environments, this combination makes external access especially difficult to secure using traditional IT-centric tools.
Not sure what secure vendor remote access is? You can read the full glossary definition in “What is Secure Vendor Remote Access?”
How Xona addresses this
Xona enables organizations to define and control third-party access through identity-based, time-limited, and protocol-isolated sessions. All access is browser-based and does not require users to be part of the internal network or identity infrastructure. External users are governed by policy, isolated from systems, and fully audited without persistent credentials or shared accounts.
Key Takeaways
Third-party and OEM access refers to external users connecting to OT or ICS systems for support, diagnostics, or maintenance.
This access is high-privilege, often unmanaged, and requires a distinct security model from internal user access.
Why is third-party access a unique cybersecurity risk in OT environments?
Third-party access introduces one of the highest-risk pathways into operational technology environments. External users often connect from unmanaged devices over untrusted networks, and their sessions may involve elevated privileges to sensitive control systems. Unlike internal users, they typically fall outside of standard IT governance, and their access is more difficult to monitor, restrict, or revoke consistently.
In OT, availability and stability are prioritized alongside security. Any unauthorized command, misconfiguration, or malware exposure introduced by a third party can have operational consequences. For example, remote access to a programmable logic controller or human-machine interface from an infected laptop can cause downtime, system damage, or safety risks. Even when access is intended for legitimate maintenance, the combination of unmanaged endpoints, elevated privileges, and limited session visibility creates a quiet but persistent exposure path that often goes undetected until after an incident or audit.
Third-party users also present a supply chain risk. Threat actors increasingly target OEMs and contractors as indirect vectors into critical infrastructure. These users often reuse credentials, share accounts across teams, and rely on VPN tunnels that offer broad access. In many environments, there is no way to verify what a vendor did, when, or why, creating audit gaps and residual exposure long after the session ends.
How Xona addresses this
Xona eliminates direct connectivity between third-party endpoints and OT systems. All access is brokered through a hardened gateway. External users connect via browser without ever reaching the control network, and their sessions are authenticated, recorded, and enforced by policy.
Key Takeaways
Third-party access in OT environments often involves unmanaged endpoints, high privileges, and limited oversight, making it a preferred target for attackers.
These access paths create operational and audit risks that traditional network-based security tools were not designed to control.
What compliance requirements govern third-party access in industrial environments?
Industrial cybersecurity regulations consistently treat third-party remote access as a high-risk function requiring specific technical and procedural safeguards. Frameworks such as NERC CIP, IEC 62443, TSA SD02E, Saudi NCA OTCC-1:2022, and NIS2 include provisions that directly apply to vendor, OEM, and contractor access.
Common requirements across these standards include multi-factor authentication, role-based access control, session recording, protocol isolation, and the ability to associate access with an authorized individual. Some also require documented access approval workflows, time-bound access windows, and revocation procedures. In many cases, these requirements apply regardless of whether the user is internal or external.
Failure to control third-party access has been a root cause of several compliance violations and audit findings. Remote access sessions without logging, credential reuse across vendors, or lack of per-session justification are among the most frequently cited gaps. In practice, many organizations attempt to satisfy these requirements through compensating controls layered onto VPNs or jump servers, but these approaches frequently fail audits because they cannot associate individual actions to a specific, authorized session with sufficient granularity.
How Xona addresses this
Xona enforces compliance-aligned controls for every remote session. External users are required to authenticate with MFA, assigned least-privilege access by role and time, and their sessions are recorded with metadata and full audit traceability. All access activity can be exported to SIEM, SOAR, or compliance platforms to support audits and reporting.
Key Takeaways
Industrial cybersecurity frameworks require strict controls over third-party access, including identity enforcement, session logging, and access governance.
Gaps in visibility, credential control, or session auditing commonly result in compliance violations related to remote vendor access.
What problems arise from legacy remote access tools in OT?
Legacy remote access tools such as VPNs, jump servers, and remote desktop gateways were designed for enterprise IT use cases and assume conditions that do not exist in OT environments. These tools were not built to account for unmanaged endpoints, protocol sensitivity, or real-time safety constraints.
VPNs create full network tunnels between remote devices and internal systems. This allows lateral movement, exposes internal services, and assumes that the endpoint is secure. Jump servers rely on shared infrastructure, offer limited protocol segmentation, and are difficult to maintain across distributed industrial sites. Agent-based tools are often incompatible with vendor devices and require installation on critical assets, which is impractical or prohibited in many OT environments.
These tools also lack session-level control. They do not restrict access by role or time, cannot enforce fine-grained resource segmentation, and often do not record sessions. As a result, it becomes difficult to prove who accessed what system, what actions they took, or whether access was authorized. Even when enhanced with MFA or privileged access tooling, these solutions still rely on persistent connectivity, endpoint trust, or shared infrastructure, which leaves OT environments exposed at the session level.
How Xona addresses this
Xona replaces legacy remote access methods with a browser-based, protocol-isolated platform that requires no network tunnels, no endpoint software, and no shared infrastructure. Every session is individually authorized, segmented by protocol, and logged in real time.
Key Takeaways
VPNs, jump servers, and other IT tools lack the controls and isolation required to secure third-party access in OT environments.
These tools assume endpoint trust and provide broad access without session-level visibility or control.
What controls are required to secure third-party access to OT and ICS systems?
Securing third-party access in OT environments requires session-level control that accounts for identity, context, and protocol. While multiple controls work together to secure third-party access, protocol isolation is the foundation that makes the rest enforceable in OT environments.
Key technical controls include:
- Multi-factor authentication to verify user identity before access is granted.
- Role-based and time-based access control to limit access to approved systems for a defined duration.
- Protocol isolation to prevent endpoints from connecting directly to OT network assets.
- Credential injection to eliminate credential sharing and persistence.
- Session recording and metadata logging to ensure accountability.
- Real-time session supervision with the ability to terminate access.
- Controlled file transfer governed by policy.
- Access approval workflows with documented justification.
- Just-in-time access with automatic expiration.
These controls work together to ensure that third-party access is auditable, restricted, and aligned with operational security requirements.
How Xona addresses this
Xona implements all required access controls in a single platform. Each session is authenticated with MFA, scoped by role and time, isolated from the control network, and governed by policy. Credentials are never shared, and all sessions are recorded and supervised.
Key Takeaways
Securing vendor access in OT environments requires session isolation, role and time restrictions, MFA, and full auditability.
These controls must operate independently of endpoint trust or internal credential sharing.
What does a secure third-party access workflow look like in OT?
A secure third-party access workflow in OT environments starts with the assumption that all external users, devices, and networks are untrusted. The goal is to enable the required task while preventing persistent access, credential reuse, or uncontrolled lateral movement. If any step in this workflow depends on shared credentials, standing access, manual cleanup, or post-session reconstruction of activity, the access model is already breaking down.
A typical secure workflow includes the following steps:
- Access request or scheduling.
- Authentication and authorization.
- Session launch through a hardened access gateway.
- Credential injection.
- Session monitoring and supervision.
- Controlled file transfer.
- Session termination and audit.
This workflow ensures that access is temporary, tightly scoped, and observable from start to finish.
How Xona addresses this
Xona automates each step of the secure access workflow in a single platform. Access is brokered without exposing internal credentials or creating network tunnels. All user actions are governed by time-limited policy, recorded in real time, and visible for supervision and audit.
Key Takeaways
A secure third-party access workflow controls the full session lifecycle.
Each session must be identity-verified, time-bound, protocol-isolated, and fully observable.
Conclusion: Rethinking third-party access to support future OT resilience
Traditional approaches to remote access were built around network perimeter models, static credentials, and trusted endpoints. In OT environments, these assumptions no longer hold.
Resilient organizations treat third-party access as a security function, not just an operational task. Instead of extending the network to the user, they isolate access at the protocol level. Instead of provisioning persistent accounts, they adopt just-in-time access. Instead of relying on trust, they enforce identity, logging, and audit for every session. This is not a tooling upgrade. It is an accountability decision.
Organizations that cannot clearly answer who accessed what system, for what purpose, and for how long are accepting risk by default.
Xona enables this transition by replacing endpoint trust and network connectivity with identity-based session control. Organizations can grant access without provisioning accounts, configure policy without firewall changes, and audit every session without relying on user-reported activity.
Frequently Asked Questions
What makes third-party access in OT environments more difficult to secure than in IT networks?
Third-party access in OT environments often involves unmanaged devices, legacy protocols, and systems that prioritize uptime and safety over frequent patching or configuration changes. Unlike IT environments, OT systems typically lack native identity governance and cannot tolerate agents or endpoint modifications. As a result, access controls must be enforceable at the session and protocol level without relying on endpoint trust or network-level access.
Why are third-party vendors and OEMs frequently targeted by attackers?
Vendors and OEMs often support multiple customers and environments, reuse credentials across teams, and connect from external networks. Attackers increasingly exploit these relationships as indirect entry points into critical infrastructure.
Can VPNs or jump servers be made secure enough for third-party access in OT?
VPNs and jump servers were not designed for OT threat models. Even when enhanced with MFA or privileged access tools, they still establish network-level connectivity and rely on endpoint trust, making them unsuitable for securing access to sensitive OT systems.
What is protocol isolation and why is it critical for OT environments?
Protocol isolation prevents third-party users from establishing direct network connections to OT systems. Users interact with systems through a session broker that mediates the protocol and presents it in a controlled interface, ensuring all activity is observable and auditable.
How does credential injection improve third-party access security?
Credential injection ensures that vendors and OEMs never see or manage internal system credentials. Authentication information is supplied only at session time, eliminating credential reuse and ensuring traceability.
How does just-in-time access reduce risk in OT environments?
Just-in-time access provisions access only when required and automatically revokes it after the approved window expires. This reduces standing privileges and limits exposure if a vendor account is compromised.
What audit evidence is typically required for third-party access in OT?
Auditors typically expect individual user authentication records, time-bound access approvals, session logs, and activity records that show what systems were accessed and when.
How should organizations handle emergency or break-glass vendor access?
Emergency access should still follow defined policies, including identity verification, session logging, and automatic expiration, without leaving persistent access in place.
Does secure third-party access require installing agents on OT systems?
A secure third-party access model should not require agents on OT systems or vendor devices. Browser-based, protocol-isolated access allows secure sessions without modifying endpoints.
What is the difference between secure vendor remote access and traditional PAM in OT environments?
Traditional PAM solutions were designed for IT systems and rely on network connectivity, credential vaulting, and agents. Secure vendor remote access focuses on session-level control and protocol isolation without extending the network or requiring agents.
Does secure third-party access apply only to vendors, or also to contractors and integrators?
Secure third-party access applies to any external user who requires access to OT or ICS systems, including contractors, system integrators, maintenance providers, and remote operations teams.
How does secure third-party access support operational resilience?
By isolating sessions, enforcing identity, and removing persistent trust, secure third-party access reduces the risk of unintended changes, malware propagation, and unauthorized activity while improving visibility and accountability.
