Protecting Legacy OT Systems: Why Segmentation and Governance Are Critical to Business Continuity
- derekdodds
- May 20
- 3 min read
In an era where digital transformation is reshaping how businesses operate, Operational Technology (OT) environments remain a crucial, but a vulnerable part of the enterprise landscape. Many organizations still rely heavily on legacy OT systems to run their production lines, logistics operations, and critical infrastructure. These systems often operate on outdated or unsupported operating systems, making them a prime target for cyber threats.
Yet, despite their importance, legacy OT systems are frequently under-protected, lacking the basic controls we take for granted in modern IT environments. In this post, we’ll explore why segregation, governance, and policy enforcement are essential to managing these aging systems and how neglecting them can lead to severe financial consequences.
1. The Risk: Legacy OT Systems Are Soft Targets
Legacy OT devices are typically designed for stability and long life cycles, not security. Many still run outdated operating systems like Windows XP, Windows 7, or even proprietary firmware that hasn’t seen a security update in years.
Because of this, they:
Often lack endpoint protection.
Can’t be patched without risking operational disruption.
Are not designed with access control in mind.
These vulnerabilities make them highly susceptible to malware, ransomware, and other attacks. And once compromised, these systems can’t easily be restored or replaced, especially if the hardware is also obsolete.
2. The Financial Impact of a Compromise
The consequences of malware infecting a legacy OT system can be catastrophic:
Production downtime: In manufacturing or logistics, even a few hours of downtime can result in millions of dollars in lost revenue.
Supply chain disruption: Compromised OT systems can disrupt downstream partners and clients, eroding trust and contractual relationships.
Costly recovery: Recovering legacy systems is not as simple as reimaging a workstation. Restoring from backup may not be feasible if modern tooling isn’t compatible, and replacement hardware may no longer be available.
Put simply: the cost of inaction is much higher than the investment in proactive security measures.
3. Segmentation: A Foundational Requirement
One of the most effective strategies for protecting legacy OT is network segmentation. By isolating these systems from the broader IT environment, you dramatically reduce the attack surface and contain any potential breach.
Segmentation best practices include:
Placing legacy OT devices in dedicated VLANs or network zones.
Using firewalls or Zero Trust gateways to strictly control communication in and out of the OT zone.
Implementing one-way traffic flows where appropriate (e.g., data diodes).
Restricting access to known, validated management stations.
Segmentation ensures that even if malware enters the IT network, it cannot easily pivot into the OT environment.
4. Policy and Governance: Clarity is Security
Effective segmentation only works when it’s backed by clear and enforceable policies. Organizations must have documented controls that define:
What OT devices can access (e.g., specific services or IP ranges).
Who can access these devices, under what conditions, and using what methods.
How they are maintained, including approved tools, patching cadence (if applicable), and change management procedures.
Without governance, these rules often become tribal knowledge or informal agreements—leaving gaps that attackers can exploit.
5. Backup and Recovery: The Hidden Challenge
Backing up legacy OT systems is not straightforward. Many backup solutions are incompatible with older operating systems or require agents that the device can’t support. In some cases, the only recovery option is a bare-metal restore from an image—if such an image even exists.
Best practices for legacy system backup include:
Using image-based backups with agentless solutions.
Storing backups offline to avoid ransomware encryption.
Validating recovery procedures periodically—not just assuming they’ll work.
If recovery isn’t possible, then prevention becomes paramount.
6. Governance Reduces Risk and Protects Revenue
Good governance around legacy OT isn’t just a security requirement—it’s a business imperative. When organizations treat these systems with the same risk management rigor as financial systems or customer data, they gain:
Improved uptime and operational continuity.
Reduced risk of revenue loss due to cyber incidents.
Greater confidence from partners, auditors, and regulators.
Ultimately, protecting legacy OT is about ensuring the business keeps running, even in the face of evolving cyber threats.
Conclusion
Legacy OT systems may not be going away anytime soon—but neither are the bad guys. Segregation, strong access controls, and documented governance policies form the core of a sustainable security strategy. While the cost of these controls may seem high, they pale in comparison to the financial and reputational damage of a compromised production environment.
It’s time to treat legacy OT not as an exception, but as a high-value asset worthy of serious protection.
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