Using CP-nets as a guide for countermeasure selection

Abstract

In this paper we present a qualitative approach for the selection of security countermeasures able to protect an IT system from attacks. For this purpose, we model security scenarios by using defense trees (an extension of attack trees) and preferences over countermeasure using Conditional Preference networks (CP-nets for short). In particular, we introduce two different methods for the composition of preferences: the and-composition and the or-composition. The first one is used to determine a preference order in the selection of countermeasures able to mitigate the risks produced by conjunct attacks. The second one is used to determine a preference order over sets of countermeasures able to mitigate the risks produced by alternative attacks.

Answer Set Optimization for and/or Composition of CP-Nets: A Security Scenario

“…The combination of defence trees and CP-nets has been recently proposed [4] as a methodology to help the system administrator to analyze a security scenario and to give him a model to represent preferences among countermeasure. The resulting structure, called CP-defence tree, integrating the CP-net described in Figure 2 is presented in Figure 2(c).…”

“…In order to find the preferred defence strategy, the approach, consisting in the composition of preferences, was proposed in [4]. More in details, two different methods establishing the preference order among the countermeasures able to stop an and-attack and an or-attack were presented.…”

“…), that can stop all the attacks to the system. To guide the selection, CP-nets [5] have been proposed to model preferences over attacks and countermeasures [4]. However, CP-nets are a graphical formalism that is good and elegant for representing small scenarios, but not so effective for big and complex scenarios.…”

“…However, CP-nets are a graphical formalism that is good and elegant for representing small scenarios, but not so effective for big and complex scenarios. In particular, the methodology proposed in [4] aims at composing together the CP-nets associated to each branch of the tree. Each CPnet, in turn, represents the preferences among the countermeasure able to stop a specific attack.…”

“…The and and or composition of the branch is then obtained by a syntactic composition of the ASO programs, whose semantics completely respects the intended meaning given in [4]. The semantics of the obtained ASO program provides a set of ordered answer sets representing the ordered sets of countermeasure to be adopted.…”