Survivability is defined as the capability of a system to fulfill its mission, in a timely manner, in the presence of attacks, failures, or accidents. Unlike traditional security measures that require central control and administration, survivability addresses highly distributed, unbounded network environments with no central control or unified security policy. Survivability focuses on delivery of essential services and preservation of essential assets, even when systems are penetrated and compromised. The focus of survivability is on delivery of essential services and preservation of essential assets during attack and compromise, and timely recovery of full services and assets following attack. Essential services and assets are defined as those system capabilities that are critical to fulfilling mission objectives.
Resistance is the capability of a system to repel attacks.
Recognition is the capability to detect attacks as they occur, and to evaluate the extent of damage and compromise. Recovery, a hallmark of survivability, is the capability to maintain essential services and assets during attack, limit the extent of damage, and restore full services following attack. The method can be applied to an existing or proposed system by a small team of trained evaluators through a structured interaction with system personnel composed of several meetings and working sessions. The method is composed of four principal steps, as follows. Essential service and asset uses are characterized by usage scenarios .