Legacy System Security
Noun · Security & Infosec
Definitions
The protection of old or unsupported systems that cannot easily be patched, upgraded, or replaced but still perform important business functions. Legacy system security often depends on isolation, strict access limits, monitoring, and compensating controls rather than ideal remediation.
In plain English: Securing old systems that are hard to update or replace.
Example: "Legacy system security for the factory controller meant network isolation and one-way access because the vendor no longer shipped patches."