Online Failure Diagnosis in Interdependent Networks

Motivation. In interdependent networks, nodes are connected to each other with respect to their failure dependency relations. As a result of this dependency, a failure in one of the nodes of one of the networks within a system of several interdependent networks can cause the failure of the entire system. Diagnosing the initial source of the failure in a collapsed system of interdependent networks is an important problem to be addressed. We study an online failure diagnosis problem defined on a collapsed system of interdependent networks where the source of the failure is at an unknown node (v). In this problem, each node of the system has a positive inspection cost and the source of the failure is diagnosed when v is inspected. The objective is to provide an online algorithm which considers dependency relations between nodes and diagnoses v with minimum total inspection cost. Methodology. We address this problem from worst-case competitive analysis perspective for the first time. In this approach, solutions which are provided under incomplete information are compared with the best solution that is provided in presence of complete information using the competitive ratio (CR) notion. Results. We give a lower bound of the CR for deterministic online algorithms and prove its tightness by providing an optimal deterministic online algorithm. Furthermore, we provide a lower bound on the expected CR of randomized online algorithms and prove its tightness by presenting an optimal randomized online algorithm. We prove that randomized algorithms are able to obtain better CR compared to deterministic algorithms in the expected sense for this online problem

Cybersecurity, our digital anchor: A European perspective

The Report ‘Cybersecurity – Our Digital Anchor’ brings together research from different disciplinary fields of the Joint Research Centre (JRC), the European Commission's science and knowledge service. It provides multidimensional insights into the growth of cybersecurity over the last 40 years, identifying weaknesses in the current digital evolution and their impacts on European citizens and industry. The report also sets out the elements that potentially could be used to shape a brighter and more secure future for Europe’s digital society, taking into account the new cybersecurity challenges triggered by the COVID-19 crisis. According to some projections, cybercrime will cost the world EUR 5.5 trillion by the end of 2020, up from EUR 2.7 trillion in 2015, due in part to the exploitation of the COVID-19 pandemic by cyber criminals. This figure represents the largest transfer of economic wealth in history, more profitable than the global trade in all major illegal drugs combined, putting at risk incentives for innovation and investment. Furthermore, cyber threats have moved beyond cybercrime and have become a matter of national security. The report addresses relevant issues, including: - Critical infrastructures: today, digital technologies are at the heart of all our critical infrastructures. Hence, their cybersecurity is already – and will become increasingly – a matter of critical infrastructure protection (see the cases of Estonia and Ukraine). - Magnitude of impact: the number of citizens, organisations and businesses impacted simultaneously by a single attack can be huge. - Complexity and duration of attacks: attacks are becoming more and more complex, demonstrating attackers’ enhanced planning capabilities. Moreover, attacks are often only detected post-mortem . - Computational power: the spread of malware also able to infect mobile and Internet of Things (IoT) devices (as in the case of Mirai botnet), hugely increases the distributed computational power of the attacks (especially in the case of denial of services (DoS)). The same phenomenon makes the eradication of an attack much more difficult. - Societal aspects: cyber threats can have a potentially massive impact on society, up to the point of undermining the trust citizens have in digital services. As such services are intertwined with our daily life, any successful cybersecurity strategy must take into consideration the human and, more generally, societal aspects. This report shows how the evolution of cybersecurity has always been determined by a type of cause-and-effect trend: the rise in new digital technologies followed by the discovery of new vulnerabilities, for which new cybersecurity measures must be identified. However, the magnitude and impacts of today's cyber attacks are now so critical that the digital society must prepare itself before attacks happen. Cybersecurity resilience along with measures to deter attacks and new ways to avoid software vulnerabilities should be enhanced, developed and supported. The ‘leitmotiv’ of this report is the need for a paradigm shift in the way cybersecurity is designed and deployed, to make it more proactive and better linked to societal needs. Given that data flows and information are the lifeblood of today’s digital society, cybersecurity is essential for ensuring that digital services work safely and securely while simultaneously guaranteeing citizens’ privacy and data protection. Thus, cybersecurity is evolving from a technological ‘option’ to a societal must. From big data to hyperconnectivity, from edge computing to the IoT, to artificial intelligence (AI), quantum computing and blockchain technologies, the ‘nitty-gritty’ details of cybersecurity implementation will always remain field-specific due to specific sectoral constraints. This brings with it inherent risks of a digital society with heterogeneous and inconsistent levels of security. To counteract this, we argue for a coherent, cross-sectoral and cross-societal cybersecurity strategy which can be implemented across all layers of European society. This strategy should cover not only the technological aspects but also the societal dimensions of ‘behaving in a cyber-secure way’. Consequently, the report concludes by presenting a series of possible actions instrumental to building a European digital society secure by design.JRC.E.3-Cyber and Digital Citizens' Securit

Connectivity in Interdependent Networks

We propose and analyze a graph model to study the connectivity of interdependent networks. Two interdependent networks of arbitrary topologies are modeled as two graphs, where every node in one graph is supported by supply nodes in the other graph, and a node fails if all of its supply nodes fail. Such interdependence arises in cyber-physical systems and layered network architectures. We study the supply node connectivity of a network: namely, the minimum number of supply node removals that would disconnect the network. We develop algorithms to evaluate the supply node connectivity given arbitrary network topologies and interdependence between two networks. Moreover, we develop interdependence assignment algorithms that maximize the supply node connectivity. We prove that a random assignment algorithm yields a supply node connectivity within a constant factor from the optimal for most networks. Keywords: Robustness; cyber-physical systems; communication networks; analytical models.United States. Defense Threat Reduction Agency (Grant HDTRA1-13-1-0021)United States. Defense Threat Reduction Agency (Grant DTRA1-14-1-0058