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Book Chapter
I. Stellios, P. Kotzanikolaou, M. Psarakis, and C. Alcaraz, "Risk Assessment for IoT-Enabled Cyber-Physical Systems",
Advances in Core Computer Science-Based Technologies, Springer International Publishing, pp. 157-173, 2021. DOI More..


Internet of Things (IoT) technologies have enabled Cyber-Physical Systems (CPS) to become fully interconnected. This connectivity however has radically changed their threat landscape. Existing risk assessment methodologies often fail to identify various attack paths that stem from the new connectivity/functionality features of IoT-enabled CPS. Even worse, due to their inherent characteristics, IoT systems are usually the weakest link in the security chain and thus many attacks utilize IoT technologies as their key enabler. In this paper we review risk assessment methodologies for IoT-enabled CPS. In addition, based on our previous work (Stellios et al. in IEEE Commun Surv Tutor 20:3453–3495, 2018, [47]) on modeling IoT-enabled cyberattacks, we present a high-level risk assessment approach, specifically suited for IoT-enabled CPS. The mail goal is to enable an assessor to identify and assess non-obvious(indirect or subliminal) attack paths introduced by IoT technologies, that usually target mission critical components of an CPS.

Conference Paper
C. Alcaraz, and S. Wolthusen, "Recovery of Structural Controllability for Control Systems",
Eighth IFIP WG 11.10 International Conference on Critical Infrastructure Protection, SRI International, Arlington, Virginia, USA , vol. 441, Springer, pp. 47-63, 2014. DOI More..


Fundamental problems in control systems theory are controllability and observability, and designing control systems so that these properties are satisfied or approximated sufficiently. However, it is prudent to as- sume that an attacker will not only be able to subvert measurements but also control the system. Moreover, an advanced adversary with an understanding of the control system may seek to take over control of the entire system or parts thereof, or deny the legitimate operator this capability. The effectiveness of such attacks has been demonstrated in previous work. Indeed, these attacks cannot be ruled out given the likely existence of unknown vulnerabilities, increasing connectivity of nominally air-gapped systems and supply chain issues. The ability to rapidly recover control after an attack has been initiated and to detect an adversary’s presence is, therefore, critical. This paper focuses on the problem of structural controllability, which has recently attracted substantial attention through the equivalent problem of the power dom- inating set introduced in the context of electrical power network control. However, these problems are known to be NP-hard with poor approx- imability. Given their relevance to many networks, especially power networks, this paper studies strategies for the efficient restoration of controllability following attacks and attacker-defender interactions in power-law networks. 

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Journal Article
J. E. Rubio, C. Alcaraz, and J. Lopez, "Recommender System for Privacy-Preserving Solutions in Smart Metering",
Pervasive and Mobile Computing, vol. 41, Pervasive and Mobile Computing, pp. 205-218, 10/2017. (I.F.: 2.974)More..


Nowadays, Smart Grid is envisaged to provide several benefits to both customers and grid operators. However, Smart Meters introduce many privacy issues if consumption data is analysed. In this paper we analyse the main techniques that address privacy when collecting electricity readings. In addition to privacy, it is equally important to preserve efficiency to carry on with monitoring operations, so further control requirements and communication protocols are also studied. Our aim is to provide guidance to installers who intend to integrate such mechanisms on the grid, presenting an expert system to recommend an appropriate deployment strategy.

Impact Factor: 2.974
Journal Citation Reports® Science Edition (Thomson Reuters, 2017)

PDF icon rubiorecommender17.pdf (461.99 KB)
J. Lopez, J. E. Rubio, and C. Alcaraz, "A Resilient Architecture for the Smart Grid",
IEEE Transactions on Industrial Informatics, vol. 14, issue 8, IEEE, pp. 3745-3753, 08/2019, 2018. DOI (I.F.: 7.377)More..


The Smart Grid offers many benefits due to the bidirectional communication between the users and the utility company, which makes it possible to perform a fine-grain consumption metering. This can be used for Demand Response purposes with the generation and delivery of electricity in real time. It is essential to rapidly anticipate high peaks of demand or potential attacks, so as to avoid power outages and denial of service, while effectively supplying consumption areas. In this paper, we propose a novel architecture where cloud computing resources are leveraged (and tested in practice) to enable, on the one hand, the consumption prediction through time series forecasting, as well as load balancing to uniformly distribute the demand over a set of available generators. On the other and, it also allows the detection of connectivity losses and intrusions within the control network by using controllability concepts.

Impact Factor: 7.377
Journal Citation Reports® Science Edition (Thomson Reuters, 2018)

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C. Alcaraz, "Resilient Industrial Control Systems based on Multiple Redundancy",
International Journal of Critical Infrastructures (IJCIS), vol. 13, no. 2/3, Inderscience Publisher, pp. 278 - 295, 11/2017. DOI More..


The incessant search for cost-effective recovery solutions for structural controllability has led to one of the most challenging research areas within the field of critical infrastructure protection. The resilience of large heterogeneous distributions, like industrial control scenarios, is proving to be a complicated mission due to the inherent non-locality problems of structural controllability and its susceptibility to advanced threats. To address these issues, this paper proposes a new repair approach based on multiple redundant pathways and the lessons learnt from the work presented in [1]. From [1], we have adapted the local measures, to combine them with each of the five strategies of remote reconnection described in this paper. To validate the sustainability of the combined approaches, two practical case studies are presented here, showing that a local dependence on a brother driver node together with remote dependence is enough to reach optimal states in linear times.

C. Alcaraz, J. Lopez, and K-K. Raymond Choo, "Resilient Interconnection in Cyber-Physical Control Systems",
Computers & Security, vol. 71, Elsevier, pp. 2-14, 11/2017. DOI (I.F.: 2.650)More..


Secure interconnection between multiple cyber-physical systems has become a fundamental requirement in many critical infrastructures, where security may be centralized in a few nodes of the system. These nodes could, for example, have the mission of addressing the authorization services required for access in highlyrestricted remote substations. For this reason, the main aim of this paper is to unify all these features, together with the resilience measures so as to provide control at all times under a limited access in the field and avoid congestion. Concretely, we present here an optimal reachability-based restoration approach, capable of restoring the structural control in linear times taking into account: structural controllability, the supernode theory, the good practices of the IEC-62351 standard and the contextual conditions. For context management, a new attribute is specified to provide a more complete authorization service based on a practical policy, role and attribute-based access control (PBAC + RBAC + ABAC). To validate the approach, two case studies are also discussed under two strategic adversarial models.

Impact Factor: 2.650
Journal Citation Reports® Science Edition (Thomson Reuters, 2017)

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R. Roman, C. Alcaraz, and J. Lopez, "The Role of Wireless Sensor Networks in the Area of Critical Information Infrastructure",
Information Security Technical Report, vol. 12, no. 1, Elsevier, pp. 24-31, 2007. DOI More..


Critical Infrastructures, such as energy, banking, and transport, are an essential pillar to the well-being of the national and international economy, security and quality of life. These infrastructures are dependent on a spectrum of highly interconnected information infrastructures for their smooth, reliable and continuous operation. The field of protecting such Critical Information Infrastructures, or CIIP, faces numerous challenges, such as managing the secure interaction between peers, assuring the resilience and robustness of the overall system, and deploying warning and alert systems, amongst others. In this tapestry of CIIP, Wireless Sensor Networks can be used as an invaluable tool due to their intelligent distributed control capabilities, alongside with their capability to work under severe conditions. In this paper, we justify why Wireless Sensor Networks technology is suitable for providing security for these scenarios, describing both their advantages and research issues and their role in the overall scheme of protecting the Critical Information Infrastructures.

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