How to Secure Legacy IT Systems in a Modern Infrastructure

Aug 13

Legacy IT systems are often the backbone of critical operations but they come with serious security risks. Outdated software, limited support, and integration challenges make them prime targets for cyber threats.

As digital transformation accelerates, organisations must secure these systems without disrupting business. In this blog, we explain how to identify legacy risks and apply modern security principles to protect your infrastructure.

Understanding Legacy Risks

Legacy systems introduce several risks:

Unpatched vulnerabilities
Unsupported software or hardware
Incompatibility with modern security tools
Limited access controls

These systems often lack encryption, centralised management, or even monitoring capabilities. Left unaddressed, they become points of failure and easy entry paths for attackers. The challenge lies in securing them without breaking mission-critical operations.

Assessing and Prioritising Assets

Start with a full asset inventory:

What legacy systems are still active?
Which ones support critical functions?
What data do they handle?

Rank systems by risk exposure and business impact. Focus first on those with internet connectivity, sensitive data, or integration points with newer systems. This prioritisation allows resource allocation based on risk, rather than convenience.

Engage IT, security, and compliance teams to assess technical constraints and regulatory responsibilities.

Applying Security Controls Without Full Replacement

Replacing legacy systems is ideal, but not always feasible. Instead, apply layered security controls:

Isolate them in segmented networks.
Apply virtual patching where physical patches aren’t possible.
Use firewalls, proxies, and secure gateways to limit exposure.
Enforce MFA and log monitoring even on outdated interfaces.
Backup data regularly and monitor for anomalies.

You can also deploy agents or wrappers that provide basic visibility and logging. The goal is to shield these systems with external defences, reducing risk while maintaining continuity.

Planning for Modernisation

While short-term controls help, long-term security depends on planned modernisation. Build a roadmap to:

Migrate to supported platforms
Move critical functions to the cloud
Replace obsolete components gradually
Secure funding and stakeholder alignment

This roadmap should align with digital transformation goals, avoiding costly one-off fixes. Documentation, vendor support, and retraining must also be considered. Modernisation doesn’t have to be disruptive but it must be strategic.

Conclusion

Legacy systems can’t be ignored but they can be secured. With the right mix of short-term safeguards and long-term planning, you can protect critical operations while evolving your infrastructure.

Techdirect helps organisations assess legacy risk and implement practical, cost-effective security strategies.

Johnny Loh