Survivability is the capability of a system to fulfill its mission in a timely manner, even in the presence of attacks or failures. Survivability goes beyond security and fault tolerance to focus on delivery of essential services, even when systems are penetrated or experience failures, and rapid recovery of full services when conditions improve. Unlike traditional security measures that require central control and administration, survivability addresses highly distributed, unbounded network environments that lack central control and unified security policies. The focus of survivability is on delivery of essential services and preservation of essential assets. Essential services and assets are 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. SNA is a practical engineering process that permits systematic assessment of the survivability properties of proposed systems, existing systems, and modifications to existing systems. The analysis is carried out at the architecture level as a cooperative project by an SEI team working with your team of system architects, developers, and stakeholders. The method proceeds through a series of joint working sessions, culminating in a briefing on findings and recommendations.