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There’s a quiet paradox at the heart of enterprise IoT: The most critical systems often rely on the oldest, least secure devices.

In healthcare, industrial control, finance, and manufacturing, legacy IoT devices remain operational because they’re essential to business processes—and replacing them is costly, disruptive, or sometimes simply not feasible. These include everything from MRI machines still running Windows XP, to factory sensors designed for closed networks, to smart meters that haven’t seen a firmware update in over a decade.

The longer these legacy devices stay online, the more risk they introduce. And unlike modern IT assets, securing them isn’t as easy as installing an agent or running a patch.

So how do you protect what you can’t easily modernize?

The hidden cost of keeping things running

Legacy IoT devices often fly under the radar, rarely touched by routine vulnerability scans or endpoint protection strategies. Unlike a Windows laptop or a mobile device, these systems can’t run antivirus software, and they may not support modern protocols like TLS 1.3 or mutual authentication.

The assumption has long been that these systems are protected by network segmentation or isolation. But segmentation alone doesn't account for lateral movement, configuration drift, or unknown changes in device behavior. Once an attacker compromises a weak IoT device, it becomes a stealthy launchpad for broader intrusion.

And when you add scale into the equation—thousands or tens of thousands of these devices scattered across environments—it’s easy to see how visibility, let alone control, becomes unmanageable without the right tools.

Why endpoint security falls short

Traditional security tooling assumes you can install an agent or push a software update. But legacy IoT devices are often constrained by design: limited CPU, minimal memory, outdated firmware, and proprietary protocols.

They weren’t built with modern cybersecurity in mind—and retrofitting protection isn’t always possible. That’s why organizations must turn to external controls and focus on visibility, segmentation, and most importantly, device identity.

How PKI helps bring legacy devices into the fold

Device authentication, backed by strong digital certificates, offers a way forward—even for unsupported devices. A certificate acts as a cryptographic passport: It doesn’t require installing endpoint software, but it does allow you to verify device identity, restrict access, and enforce time- or behavior-based policies.

While public key infrastructure (PKI) might sound like overkill for a small sensor or badge reader, it’s a proven model for securing critical systems, from medical devices to industrial controls. Its ability to deliver strong, scalable device identity makes it especially well-suited for IoT environments, where traditional endpoint protection simply doesn’t apply.

With PKI, organizations can verify device legitimacy, encrypt data in transit, and enforce access controls—even on devices that can’t run agents or support modern OS features. Certificate-based identity allows you to:

• Ensure only authorized devices connect to critical systems.

• Enforce authentication before allowing data exchange.

• Build audit trails around device interactions—something older systems rarely provide natively.

With platforms like ¶ºÒõ¹Ý® ONE, organizations can automate certificate lifecycle management, integrate with Network Access Control (NAC) and Zero Trust policies, and manage the lifecycle of IoT credentials without touching the device itself.

Reducing policy chaos

One of the key problems with legacy IoT devices is the operational overhead required to manage them. Network segmentation requires detailed policy rules—what the device can talk to, how, and when. Those rules are fragile. One change to a device’s function or location can cascade into misconfigurations or create gaps attackers can exploit.

But when you introduce certificate-based identity, you reduce reliance on manual network policies. Access decisions are made based on verified identity and posture, not static IPs or zones. You move from policy sprawl to adaptive trust, streamlining management and increasing resilience at the same time.

Acting before regulation catches up

The regulatory landscape is shifting fast. The EU Cyber Resilience Act, U.S. Executive Orders, and industry-led efforts like the ioXt Alliance are raising the bar on device-level security—and that includes legacy assets. Increasingly, enterprises will be expected to secure all connected devices, regardless of age or updateability.

Organizations that wait for mandates risk scrambling later. But those who implement flexible, identity-driven security now are better positioned to meet future compliance requirements—and prevent incidents before they happen.

Smarter PKI, stronger outcomesÌý

Legacy systems don’t just pose security risks—they drain time, budget, and resources. Forward-thinking organizations are gaining a competitive advantage by turning certificate chaos into streamlined, secure operations with ¶ºÒõ¹Ý ONE.Ìý

Read Forrester’s Total Economic Impact™ study to see the ROI of getting ahead of IoT risk.