Loss of availability is a security impact in which a system, device, or service cannot be used as intended. In cyber security, it covers outages, shutdowns, lockouts, and control failures that prevent normal operation. In industrial environments, availability is often the most important security objective because even a short interruption can stop production, disable monitoring, or interrupt safety functions.
This matters in OT and ICS settings because operators depend on SCADA, PLCs, and remote-access links to keep physical processes stable. Attackers may cause loss of availability through denial-of-service traffic, ransomware, destructive malware, credential abuse, or manipulation of control systems. Defenders reduce the risk with network segmentation, strong access controls, redundant systems, tested backups, and recovery plans. In practice, a cyber incident does not need to steal data to be serious; if it prevents the process from running, it has already achieved a major impact.