How should critical infrastructure teams reduce risk when remote access to operational technology is still necessary?

How to reduce OT remote-access risk without breaking operations

Remote access is often unavoidable in operational technology environments, but the risk profile changes once external connectivity exists. The practical goal is to shrink exposure before you harden permissions: minimise direct internet reachability, keep access paths narrow, and make every connection attributable. For critical infrastructure teams, that means treating remote access as a controlled exception, not a convenience layer.

One useful lens is that the biggest failures usually come from overly broad connectivity, not from the mere fact that remote access exists. NHIMG’s key challenges and risks guidance is relevant here because remote support channels often inherit the same visibility, overprivilege, and lifecycle weaknesses that create account and credential exposure elsewhere. The same control logic also shows up in OT-specific guidance such as NIST SP 800-82 Rev 3, OT Security Guide and CISA Industrial Control Systems, both of which emphasise segmentation, controlled access paths, and careful handling of external connectivity.

• Remove any remote path that is not tied to an active operational need.
• Prefer a brokered access model over direct inbound exposure to OT assets.
• Limit who can connect, which assets they can reach, and what commands or actions are allowed.
• Make sessions visible and reviewable so support activity can be audited after the fact.
• Separate emergency repair access from routine access so “temporary” does not become standing privilege.

What good OT remote access looks like in practice

A defensible design starts with identity and access discipline, then layers on segmentation and monitoring. Remote users and third parties should reach only the specific jump point or broker they need, not the plant network broadly. Privileged access controls matter because OT support is frequently done by high-value accounts that can touch many systems quickly, so least privilege and just-in-time access reduce blast radius when those accounts are abused or misused.

This is also where OT teams should be precise about session controls. Recording or live supervision is valuable only if the session can be tied to a named person, a ticket or work order, and a defined maintenance window. If the connection is invisible, shared, or reusable, then incident response loses the ability to reconstruct what happened. The CIS Controls v8 and NIST SP 800-207 Zero Trust Architecture both reinforce this pattern: verify explicitly, limit lateral reach, and avoid assuming that a trusted path stays trustworthy just because it is familiar.

Decision rule: If the remote session can reach production OT control functions, treat it like privileged access and require strong approval, scope limits, and session visibility. If it is only for vendor troubleshooting, scope it to the minimum set of hosts and time windows needed, then revoke it immediately after use.

What to verify: Teams should be able to prove that every external connection is tied to an owner, an asset, and a business justification. They should also be able to show that standing access is reviewed, that emergency access expires, and that third-party access is removed when support ends.

Risk and Threat Considerations

Remote access becomes dangerous when a support channel turns into a persistent foothold. The main exposure is not just unauthorised entry, but the combination of broad reach, weak monitoring, and long-lived privilege that lets an attacker or careless operator move from a remote support path into critical OT functions.

Failure mechanism: Compromised credentials, exposed remote services, or overbroad vendor accounts can be used to authenticate into OT-adjacent systems, then pivot deeper because the access path was designed for convenience rather than containment.

Impact: The result can be unauthorised control actions, service interruption, safety risk, or a wider incident if the same access path reaches multiple sites or enclaves. In critical infrastructure, a single weak remote access channel can become a high-impact dependency.

Practitioner Guidance

What to prioritise: Start with the access path itself. If you can eliminate direct internet exposure or replace it with a brokered, time-bound route, you reduce risk more than by tuning downstream permissions alone.

What to measure: Track the number of standing remote-access entitlements, the percentage of sessions with named ownership and ticket linkage, and how quickly temporary support access is revoked after use.

Common mistake: Treating vendor urgency as a reason to leave access open. In OT, the highest-risk pattern is usually “temporary” access that never gets removed, especially when it includes administrative reach.

Practitioner takeaway: The safest remote-access model is one that is narrow, attributable, and expiring, because in OT the real risk is not remote access itself, but remote access that can persist, spread, or act without accountability.

Related resources from NHI Mgmt Group

• How should security teams reduce infrastructure access risk when shared logins and shared keys are still in use?
• Why does just-in-time access reduce operational risk for remote engineering teams?
• How should security teams reduce breach risk when remote access still depends on passwords and weak MFA factors?
• How should security teams reduce ransomware risk in factory environments that still depend on Windows systems and shared operational access?