Multi-step Attack Modelling and Simulation (MsAMS) Framework Based on Mobile Ambients

Attackers take advantage of any security breach to penetrate an organisation perimeter and exploit hosts as stepping stones to reach valuable assets, deeper in the network. The exploitation of hosts is possible not only when vulnerabilities in commercial off-the-shelf (COTS) software components are present, but also, for example, when an attacker acquires a credential on one host which allows exploiting further hosts on the network. Finding attacks involving the latter case requires the ability to represent dynamic models. In fact, more dynamic aspects are present in the network domain such as attackers accumulate resources (i.e. credentials) along an attack, and users and assets may move from one environment to another, although always constrained by the ruling of the network. In this paper we address these dynamic issues by presenting MsAMS (Multi-step Attack Modelling and Simulation), an implemented framework, based on Mobile Ambients, to discover attacks in networks. The idea of ambients fits naturally into this domain and has the advantage of providing flexibility for modelling. Additionally, the concept of mobility allows the simulation of attackers exploiting opportunities derived either from the exploitation of vulnerable and non-vulnerable hosts, through the acquisition of credentials. It also allows expressing security policies embedded in the rules of the ambients.