Resilience vs. reliability vs. security

These three terms are often used interchangeably but describe distinct properties. Reliability is the ability of a system to withstand instability, uncontrolled events, cascading failures, or the unanticipated loss of components. Resilience is the ability to adapt to changing conditions and recover rapidly from a disruption once it happens. Security specifically refers to the ability to withstand deliberate attacks, physical or cyber, on a system's integrity and operations. A system can be highly reliable under normal conditions yet not resilient to an unprecedented event, and neither reliability nor resilience by itself guarantees security against a deliberate attacker.