Redundancy Planning for Cost Efficient Resilience to Cyber Attacks

Abstract

We investigate the extent to which redundancy (including with diversity) can help mitigate the impact of cyber attacks that aim to reduce system performance. Using analytical techniques, we estimate impacts, in terms of monetary costs, of penalties from breaching Service Level Agreements (SLAs), and find optimal resource allocations to minimize the overall costs arising from attacks. Our approach combines attack impact analysis, based on performance modeling using queueing networks, with an attack model based on attack graphs. We evaluate our approach using a case study of a website, and show how resource redundancy and diversity can improve the resilience of a system by reducing the likelihood of a fully disruptive attack. We find that the cost-effectiveness of redundancy depends on the SLA terms, the probability of attack detection, the time to recover, and the cost of maintenance. In our case study, redundancy with diversity achieved a saving of up to around 50 percent in expected attack costs relative to no redundancy. The overall benefit over time depends on how the saving during attacks compares to the added maintenance costs due to redundancy.

A Hybrid Threat Model for Smart Systems

“…Further approaches have considered how to associate the attack progression through the system to its impact on the system model (e.g. [19]). It is then possible to conduct a cost based analysis to identify the most cost effective countermeasures or to evaluate the cost effectiveness of different mitigating strategies.…”

“…For example, when system elements are compromised, this can be taken into account and the new probabilities of compromise can be calculated [22], [17]. The new probabilities of compromise can be used to choose countermeasures [23] and can also be combined with system models and cost models for resilience analysis as shown in [19]. However, our focus here is on the analysis and the generation of the graph for hybrid systems and we leave such extensions for further work.…”