Degraded-mode operation is a system’s ability to continue functioning with reduced capability when an input, component, or connection fails. Rather than operating normally, it may rely on fewer sensors or limited functions while attempting to remain safe and useful.
In cybersecurity and safety-critical systems, this behavior matters because attacks or outages can disrupt communications, navigation, or other essential inputs. For example, a drone might use onboard sensors when satellite navigation is unavailable, yet still face a separate loss of its operator link. Defenses should define what functions remain available, what limits apply, and whether the system should continue, enter a safe state, or stop. Testing these failure conditions helps reveal whether resilience claims match actual behavior.