Fault tolerance is a design approach that keeps a system operating when one or more components fail. Instead of stopping at the first error, a fault-tolerant system isolates the failure, reroutes work, or falls back to a safe mode. Common techniques include redundancy, automatic failover, retries with limits, and graceful degradation.
In cyber security, fault tolerance matters because outages can be as damaging as breaches. Attackers often exploit single points of failure by targeting servers, identities, networks, or dependencies. A fault-tolerant architecture reduces that blast radius and helps defenders maintain service during DDoS attacks, hardware crashes, software bugs, or partial compromise. It also supports incident response: logs, backups, and redundant control paths can keep security tools available when one layer fails. Good fault tolerance does not hide errors; it ensures the system remains predictable, recoverable, and safe under stress.