Why Vendor Security Questionnaires Fail in OT

In OT and ICS (Industrial Control Systems) environments, vendor risk management is a foundational pillar of cybersecurity. Yet, despite best intentions, vendor security questionnaires, the most common tool for supply-chain risk assessment, routinely fail to deliver meaningful, actionable insight. The result is a false sense of security that jeopardizes the availability, integrity, and safety of industrial operations. To understand why, we must examine both the unique realities of OT and the inherent limitations of the questionnaire approach.

1. OT Is Not IT: The Wrong Paradigm

Traditional security questionnaires are built on IT assumptions:

Patching cadence exists.
Standard encryption and authentication are always feasible.
Network segmentation and endpoint controls behave predictably.

In OT, these assumptions are invalid. Many ICS components:

Cannot be patched without operational risk.
May rely on proprietary protocols (e.g., Modbus, DNP3) with no native security.
Operate legacy firmware that cannot be updated.
Must run 24/7 with zero downtime tolerance.

A questionnaire that asks whether a vendor supports quarterly patching or endpoint agents ignores these contextual constraints. The result: the answers reflect an IT scorecard, not actual OT risk.

2. The Illusion of Compliance Over Actual Risk

Vendor questionnaires are inherently checkbox-driven:

✔ Do you have MFA?
✔ Are logs retained for 90 days?
✔ Do you encrypt data in transit?

These controls are meaningful in IT, but in OT:

MFA may be non-existent due to device limitations.
Logging may not be possible without disrupting real-time control loops.
Encryption might conflict with latency tolerances or deterministic communication requirements.

A vendor may respond “Yes” because they interpret the question generously, or because they append compensating controls. But compliance ≠ security, especially in OT where the impact of misconfiguration can be safety-critical.

3. Lack of Domain-Specific Understanding

Many questionnaires are written by GRC or procurement teams with minimal OT expertise. Typical questions assume:

Standardized hardware and software lifecycles.
Homogeneous environments.
Cloud-native architectures.

OT environments, by contrast, are:

Highly heterogeneous (PLCs, RTUs, HMIs, DCS, legacy devices).
Often air-gapped or connected via unidirectional gateways.
Embedded with custom logic that cannot be abstracted into simple metrics.

Without OT domain fluency, the questionnaire becomes a collection of buzzwords, not a risk instrument.

4. Self-Assessment Bias and Lack of Verifiability

Vendor responses to security questionnaires are self-reported. There is no inherent mechanism to verify:

Whether the vendor actually performs network segmentation.
Whether their cryptographic keys are properly managed.
Whether their development lifecycle includes threat modeling for ICS threats.

In OT, where process safety and functional safety intersect with cybersecurity, unverified claims are toxic. A vendor might claim “secure by design” while their product still exposes unfiltered Ethernet traffic or default credentials.

5. Static Questionnaires in a Dynamic Threat Landscape

Threat actors targeting OT are sophisticated and constantly evolving their Tactics, Techniques, and Procedures (TTPs). Questionnaires rarely update at the pace of threats like:

Supply-chain compromise
Firmware tampering
Protocol-aware manipulation
Insider threats targeting engineering workstations

Static questionnaires cannot anticipate emerging attack vectors. As a result, they become obsolete as soon as they’re signed off.

6. False Equivalence of Controls Across Domains

A question like “Do you use TLS 1.2+?” assumes that encryption technology universally improves security. In OT:

Some protocols cannot be encapsulated in TLS without redesign.
Adding encryption may introduce timing variances that destabilize process control.

Thus, vendors may answer “Yes” based on IT practices, but such controls may be impractical or even harmful in an OT context.

7. Lack of Risk Context and Impact Modeling

OT environments are uniquely about safety, continuity, and physical effects. A typical questionnaire does not quantify:

The impact of a compromised remote access channel on plant shutdown.
The safety implications of a manipulated PLC output.
The operational cost of a false positive intrusion detection alert.

Without a risk context, vendors can satisfy requirements without actually reducing enterprise risk.

8. Organizational Misalignment

Vendor questionnaires often originate in procurement or compliance, not in OT cybersecurity leadership. This creates:

Misaligned priorities (contract obligations over operational risk).
Abstract questions divorced from engineering realities.
Acceptance of generic answers due to a lack of technical challenge.

The consequence: Organizations believe they “checked the box” while their assets remain exposed.

9. The Rise of Connected Supply Chains Without Commensurate Controls

Digital transformation has connected OT systems with enterprise and cloud environments. Vendors increasingly integrate:

Remote diagnostics
Telemetry and analytics
Over-the-air updates

Yet questionnaires rarely evaluate:

Third-party access controls
Segmentation of engineering networks
Secure update pipelines

This blind spot is a driver of high-impact incidents like supply-chain breaches that propagate into OT.

10. The Need for Evolution: Beyond Questionnaires

To genuinely assess OT vendor risk, organizations must move toward adaptive, evidence-based assessments:

Technical Assessments

On-site network traffic analysis
Firmware and binary analysis
Active probing with OT-safe techniques

Threat-Informed Risk Modeling

Mapping vendor components to MITRE ATT&CK for ICS
Prioritizing controls based on likelihood and consequence

Continuous Monitoring

Telemetry from vendor interfaces
Behavioral anomaly detection
Validation of vendor claims against actual performance

Conclusion: Questionnaires Are Not Enough

Vendor security questionnaires in OT fail not because they are poorly written, but because they apply the wrong paradigm to the wrong domain. OT environments demand contextualized, evidence-backed, and risk-centric evaluation. Unless we evolve our approach from tick-the-box compliance to domain-specific risk intelligence, industrial enterprises will continue to suffer breaches that start with a confident “Yes” on a form and end with an unexpected outage, or worse, a safety incident with real-world consequences.

Search This Blog

AI-powered ICS/ OT Cybersecurity