Critical digital infrastructure is the set of systems, networks, applications, and cloud services that support essential operations. If these systems fail, the impact can extend beyond one organization and disrupt public services, business continuity, or the wider economy. In practice, this includes identity systems, communications platforms, payment processing, industrial control environments, and the cloud workloads that keep them available.
This term matters in cyber security because attackers often target critical infrastructure to maximize pressure, disruption, or leverage. Ransomware, supply-chain compromise, denial-of-service attacks, and privileged access abuse can all affect these systems. Defenders treat them differently from ordinary IT: they require stronger segmentation, redundancy, backup and recovery testing, access controls, monitoring, and clear governance. In cloud settings, the key question is whether the organization can still operate, restore, and move workloads when a provider, region, or dependency becomes unavailable.