What should critical infrastructure teams do when remote vendor access is unavoidable?

When remote vendor access cannot be avoided, what boundary should teams enforce?

Remote vendor access should be treated as a tightly bounded exception with explicit scope, time limits, and monitored destinations. The safest posture is to define exactly what the vendor can reach, why that access exists, and when it expires. Anything broader turns a support path into an uncontrolled trust relationship that can become an operational pathway into critical systems.

That boundary should be narrow enough that the vendor can complete the approved task without opening a route to adjacent control environments, engineering tools, or administrative surfaces. If the access model cannot express that constraint clearly, the problem is not the vendor, it is the access design.

For critical infrastructure teams, the practical question is not whether the vendor is legitimate, it is whether the session is constrained to the smallest workable blast radius. Third-Party, B2B and Contractor Access Guide is useful here because it frames sponsorship, least privilege, time limits, and review as the baseline for external access governance. Remote Access Identity Guide is the clearer fit when the concern is VPN risk, ZTNA, and retiring broad remote entry paths.

How should access be scoped so it cannot spread beyond the intended task?

Scope the vendor to approved use cases, named assets, and the minimum set of interfaces needed to finish the job. If a vendor only needs to troubleshoot one platform, do not let the session wander into the broader OT or IT estate, even if the same network path technically permits it. Scoping should be enforced by policy and architecture, not just by a ticket description.

In operational environments, the strongest control is usually a combination of segmentation, destination restriction, and role separation. OT and ICS Identity and Access Guide aligns well with that need because it addresses vendor remote access, shared accounts, PAM, and zones-and-conduits thinking. When the access path is designed around task boundaries rather than convenience, lateral movement becomes much harder to convert into control-system impact.

The access model should also be reviewed for exceptions that have quietly become permanent. A vendor connection that started as a short-term workaround but now exists as a standing pathway is usually a sign that scope has drifted faster than governance.

Why do remote vendor paths become an outage or intrusion problem?

The risk is that a vendor session often sits close enough to privileged systems to bypass normal friction, yet broad enough to expose assets that were never part of the original business need. Once an attacker, stolen credential, or abused support channel gets into that path, the same convenience that helped the vendor operate can help an adversary move laterally.

That is why remote support needs stronger handling than ordinary user access. Privileged Session Management Guide is a good reference point for brokering, recording, and controlling admin sessions, which is especially relevant when third-party access can affect high-impact systems. Colonial Pipeline ransomware attack remains a sharp reminder that dormant or under-controlled remote access can have consequences far beyond the login itself.

Vendor access also tends to fail in predictable ways: credentials persist too long, approvals are vague, and monitoring focuses on connection success instead of reachable assets. When that happens, the access path becomes a standing trust bridge rather than a controlled support exception.

Risk and Threat Considerations

Remote vendor access is attractive to attackers because it often combines trust, privilege, and operational urgency in one channel. If the connection is broad, a compromise of the vendor account, remote tool, or supporting credential can turn into lateral movement, service disruption, or direct manipulation of control systems.

Failure mechanism: The access path remains more powerful than the task it was created to support, so a stolen login, reused credential, or abused support session can reach systems that should have been unreachable from that channel.

Impact: A single remote foothold can expand into operational disruption, loss of integrity in critical processes, or a wider incident that is harder to contain because the vendor path was never tightly bounded.

Practitioner Guidance

What to verify: Confirm that every vendor path has a named sponsor, an approved use case, an expiry condition, and a documented destination list. If any of those are missing, treat the access as incomplete governance, not an acceptable temporary convenience.

What good looks like: The vendor can reach only the specific jump point, host, or application needed for the task, with session oversight strong enough to prove what was touched and when. Change Healthcare breach 2024 and SonicWall SSL VPN account compromises 2025 both reinforce the judgment that remote access becomes material risk when strong identity controls are absent or too broadly trusted.

Decision rule: If the vendor session can reach production control assets that are not required for the work, shrink the path before widening oversight. If the access cannot be constrained without breaking the operating model, redesign the access architecture rather than accepting a standing exception.

Practitioner takeaway: The objective is not to make remote vendor access impossible, it is to make it narrow enough that a legitimate support session cannot silently become an operational blast radius.

Related resources from NHI Mgmt Group

• How should critical infrastructure teams reduce risk when remote access to operational technology is still necessary?
• How should security teams prepare access management for quantum-safe remote connections in critical infrastructure?
• How should security teams run access reviews for non-human identities?
• How should security teams govern non-human identities that have persistent access?