Successful attacks are nearly inevitable as sophisticated threat actors are committed to inflicting damage, leaving digital and physical destruction in their wakes. As defenders recognize the inevitability of successful attacks, they must change their defense paradigms from only preventing attacks to also weathering the attacks that penetrate first-line defenses. Instead, the systems' abilities to provide functionality should be minimally disrupted while simultaneously containing an attacker. The engineering challenge is to build and operate systems that are resilient to attack, able to adapt to trade off some functionality to preserve trust in more-critical functionality. We refer to this concept as graceful degradation. Defenders would be in a far better position to address the increasingly dire situation confronting them if they had a method and tool to support graceful degradation. However, this requires the ability to reason despite uncertainties at architecture and design time and at run time. Automation can be supported by formal modeling of systems, but it must not be labor-intensive. We propose and develop an approach that directly addresses these challenges. We can architect and operate systems that are better able to weather attacks by automating the evaluation of systems' security properties to enable effective automated graceful degradation of systems in the presence of uncertainty through an approach of formally modeling systems and system behavior at an architectural level of abstraction to explore hypothetical attacks and the systems' abilities to respond. We describe our approach and provide tooling to demonstrate our concept.

116 pages

Thesis Committee:
David Garlan (Co-Chair)
Matt Fredrikson (Co-Chair)
Jonathan Aldrich
LTG Peter Kind (USA, Ret.)

Nicolas Christin, Head, Software and Societal Systems Department
Martial Hebert, Dean, School of Computer Science

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