Why Third-Party Access to OT Environments Requires Stronger Security Controls

Third-party access to operational technology (OT) environments has become a major cybersecurity risk for industrial organizations. In sectors such as manufacturing, utilities, and critical infrastructure, companies often rely on dozens (and sometimes hundreds!) of external vendors, contractors, and technicians to maintain and support operational systems. These third parties provide essential expertise that many organizations cannot staff or scale internally.

But granting third-party users access to OT, industrial control systems (ICS), and cyber-physical systems (CPS) dramatically expands the attack surface and increases the likelihood of human error. This risk is especially acute when access is provided through traditional methods that rely on implicit trust, offer limited visibility, and grant broader privileges than vendors actually need. As a result, third-party access has become a leading source of cyber, operational, and safety risk in industrial environments. This article explains why industrial enterprises have become so reliant on third-party vendors, and why securing third-party access requires strong, OT-specific security controls.

Why Are Industrial Organizations So Dependent on Third-Party Vendors?

In many industrial environments, dependence on third-party vendors is not optional but operationally unavoidable, driven by expertise gaps, efficiency requirements, and contractual obligations. Indeed, collaborations with third-party partners, technicians, and other specialists are integral to the success and sustainability of industrial operations. The specific reasons for hiring external contractors will of course vary from company to company, but working with third-party vendors has a broad range of advantages.

How Specialized Expertise Drives Reliance on Third-Party OT Vendors

Industrial processes have grown increasingly complex, necessitating more specialized skills and knowledge. External vendors and contractors are likely to bring with them a wealth of experience, honed by working with a variety of clients with different needs and expectations. This subject matter expertise can be instrumental in helping organizations optimize processes or overcome technical challenges that the in-house team lacks the experience or training to solve. 

How Third-Party Contractors Help Optimize Industrial Resources

External support enables industrial enterprises to allocate their resources more effectively. Rather than maintaining an in-house team for every conceivable task, organizations can tap into the skills and resources of external vendors on a project-specific basis. This results in a leaner organizational structure, reducing overhead costs and enhancing overall efficiency. 

Why Flexibility and Scalability Require External Support 

Industrial enterprises frequently encounter fluctuations in demand, project scope, and market conditions. Beyond resource optimization, external vendors provide a level of flexibility and scalability that is challenging to achieve with a fully internal workforce. Whether it's scaling up production during peak periods or downsizing during quieter ones, the ability to adapt quickly to changing circumstances can be a key competitive advantage. 

How Cost Efficiency Makes Third-Party Vendors a Strategic Choice

Collaborating with external vendors allows organizations to leverage economies of scale that may not be achievable with in-house operations. Because they serve multiple customers, vendors can spread costs across a broader base, leading to more cost-effective solutions and services. This cost efficiency is often reflected in competitive pricing, ultimately benefiting the client’s bottom line. 

When Contractual and Warranty Requirements Mandate Third-Party Collaboration

It should now be much clearer why industrial enterprises depend so heavily on the services of external third parties. Still, it’s worth pointing out that sometimes the reason is even simpler. Manufacturers of specific OT systems or equipment often require that only members of their own workforce can service said equipment. Should an in-house technician attempt to access a system or perform a maintenance check, it could void the product warranty and create a host of additional problems. In cases like these, enterprises have literally no choice but to work with the vendor whose equipment they are operating.  

What Makes Third-Party Access to OT Environments So Risky?

There is no question that third-party collaborations bring tremendous value to industrial organizations across sectors. The problem is that allowing external vendors and contractors to access sensitive cyber-physical systems can create serious risks for the organization. And in OT and industrial environments, these risks extend beyond data loss to include operational downtime, equipment damage, and physical safety hazards.

But why exactly do third parties pose more risk than internal workers? First, vendors are not bound by the same internal security policies as direct employees. Second, they are likely to be working on their own unmanaged devices. And perhaps most significantly, legacy remote access tools generally give IT and security teams limited ability to control or even monitor vendors' actions inside the OT network.

1. How Over-Privileged Vendor Access Exposes OT Systems 

Even organizations that follow the principle of least privilege when granting access to employees may be more lax when extending access permissions to third-party vendors. Time is often of the essence when onboarding new contractors, and this can lead to their being given overly wide access to internal systems. But saving a bit of time by not configuring proper access policies for third parties can end up being very costly if this over-permissioned access leads to an operational shutdown or data breach.  

2. Why Remote Vendor Access as an Entry Point for Ransomware

When third-party devices are unmanaged and identity-based access with continuous authorization is not enforced, external vendors can introduce malware or ransomware into their clients’ infrastructure, potentially disrupting operations, causing safety incidents, or resulting in ransom demands. 

3. Why Third-Party Access Increases the Risk of Data Leakage

Contractors may intentionally or inadvertently leak sensitive information, leading to intellectual property theft, corporate espionage, or exposure of critical data. 

4. How Compromised Vendors Enable Supply Chain Attacks on OT Systems

If a vendor is compromised, attackers may use their access to target the critical infrastructure they serve, creating cascading risk and a pathway for larger-scale attacks. 

5. How Social Engineering Exploits Trusted Third-Party Relationships

Malicious actors could exploit relationships with third-party vendors to gain unauthorized access to OT environments, posing a direct threat to safety as well as security. 

6. When Inadequate Third-Party Training Creates Operational and Safety Risks

Third-party vendors are often brought on-board because of their specialized skills, but this is not always the case. Contractors who lack the necessary familiarity with safety protocols or particular equipment increase the likelihood of accidents that could halt operations and jeopardize physical safety.

How Can Organizations Secure Third-Party Access to OT Environments?

So, if businesses depend on third-party collaborations but those collaborations introduce significant inherent risks, what is the way forward? In OT environments, the challenge is not whether to allow third-party access, but how to do so without expanding the attack surface or compromising safety. Securing third-party OT access requires replacing network-level trust with identity-based, application-level access, least-privilege controls, continuous authorization, and strong oversight capabilities.

Why Agentless Access Is Essential for Securing Third-Party OT Users

Agents are pieces of installed software that run in the background of our devices, and they’re necessary for the operation of many remote access solutions (VPNs are a perfect example). There’s nothing innately wrong with agents, but they are problematic when it comes to third-party access security. The issue is that vendors likely work with many companies, and it’s unrealistic to expect them to download and then work via a different agent for each of their clients. In light of this, the ideal secure remote access solution will be agentless, with no software downloads or installations required for third-party users. 

How Zero Trust, MFA, and Continuous Authorization Protect OT Access

Zero trust is a security framework that requires every identity (whether user or device) to be identified, authenticated, and continuously authorized in order to gain and maintain access to approved applications. Multi-factor-authentication (MFA) is an added layer of identity verification that usually accompanies zero-trust access. By enforcing zero-trust access with MFA for third-party vendors and contractors, organizations can better protect themselves against credentials theft, phishing, and other common cyberattack vectors. 

Why Application-Level Access Is Safer Than Network-Level Access in OT

As noted above, over-permissioning external vendors with access they don’t actually need is a recipe for disaster. To prevent third parties from reaching data and systems beyond the scope of their work, the principle of least privilege should always be used to determine access permissions. In addition, access should be granted directly to applications and never to the full network. Prohibiting network-level access limits the damage that can be done should an unauthorized actor manage to gain access and is key to preventing the spread of ransomware and other malware.

How Access Controls and Real-Time Oversight Reduce Third-Party OT Risk

A major reason why third-party access is so risky is that organizations typically have little visibility into what these users are doing after being granted access. The solution here is to implement robust access and oversight controls that give IT and security teams the power to limit third-party access privileges (for instance, blocking the ability to copy-paste) and monitor third-party sessions in real-time.

The Future of Third-Party Access and Collaboration 

Third-party vendors and contractors are a crucial extension of the team for many if not most modern industrial enterprises, and their importance is not going to decline any time soon. Organizations must therefore take the necessary steps to mitigate the risks that third parties pose.  

The Cyolo PRO (Privileged Remote Access) advanced remote access solution was purpose-built to overcome the challenges of both third-party access and OT systems access. With Cyolo, security teams can regain control over the third-party users and devices inside their systems, allowing organizations to enjoy the numerous benefits of these relationships without the added risk. 

To learn more, read the recent white paper, “From Blind Trust to Full Visibility: How to Take Control of Third-Party OT Access.”

Frequently Asked Questions About Third-Party OT Access Security