Problem Statement
• Computer networks and Information infrastructures have become critical elements of modern society and their breakdown could cause catastrophic damages to our society and national security.
• Example of cyber infrastructure includes national defense system, air traffic control systems, power grid, food manufacturing prcesses, etc.
• Survivable system must continue to provide essential services regardless of attack, failure, disaster or accident events.

Survivability Properties
To maintain system's capabilities to deliver essential services, survivable systems must exhibit the four key properties.
• Resistance: strategies repelling attacks
• Recognition: detecting attacks and understand the current state of the system
• Recovery: restoring compromised information or functionality, restoring essential services
• Adaptation and evolution: improving system survivability based on knowledge gained

Survivability Modeling & Analysis Overview
• Survivability Definition*: Survivability is the capability of a system to deliver essential services, in a timely manner, in the presence of attacks, failures, or accidents.
• Survivability of a system depends on it's ability to resist, recognize and recover fwith respect to all types of attack, failure and accident scenarios.
• Survivability Index(SI) is a function of 3R

SI = f (Resistance, Recognition, Recovery)

SEA Framework
SEA framework is consisted of three componet blocks.
• External Events Database(EED) contains events scenarios such as DDoS attack or brute force attack for the password. The scenarios are described with sub-missions that an attacker might conduct sequentially.
• Survivability Model(SM) is an abstract of the system that we want to evalute. The model will be described in Moarkov chain wiht 3Rs rescribed on above section.
• Survivability Index(SI)'s roll is the evaluation of the modeled system with the inputs from EED and gives a feedback to SM to improve the functionality of the system under the abnormal situation. After evaluation, the recommended strategies are feeded to the SM.

*R.J. Ellison et. al., "Survivable Network Systems: An Emerging Discipline", CMU/SEI-97-TR-013