@article {alcarazlopez-IEEESystems-2017, title = {A Cyber-Physical Systems-Based Checkpoint Model for Structural Controllability}, journal = {IEEE Systems Journal}, volume = {12}, year = {2018}, month = {12/2018}, pages = {3543-3554}, publisher = {IEEE}, abstract = {

The protection of critical user-centric applications,\ such as Smart Grids and their monitoring systems, has become\ one of the most cutting-edge research areas in recent years.\ The dynamic complexity of their cyber-physical systems (CPSs)\ and their strong inter-dependencies with power systems, are\ bringing about a significant increase in security problems that\ may be exploited by attackers. These security holes may, for\ example, trigger the disintegration of the structural controllability\ properties due to the problem of non-locality, affecting, sooner\ or later, the provision of the essential services to end-users.\ One way to address these situations could be through automatic\ checkpoints in charge of inspecting the healthy status of the\ control network and its critical nature. This inspection can be\ subject to special mechanisms\ composed of trustworthy cyberphysical\ elements\ capable of detecting structural changes in the\ control and activating restoration procedures\ with support for\ warning. This is precisely the aim of this paper, which presents\ a CPSs-based checkpoint model with the capacity to manage\ heterogeneous replications that help ensure data redundancy,\ thereby guaranteeing the validity of the checkpoints. As a support\ to this study,\ a theoretical and practical analysis is addressed to\ show the functionality of the approach in real contexts.

}, keywords = {Critical Control Systems, cyber-physical systems, Smart grids, structural controllability}, issn = {1932-8184}, doi = {https://doi.org/10.1109/JSYST.2017.2740719}, url = {http://ieeexplore.ieee.org/document/8057984/}, author = {Cristina Alcaraz and Javier Lopez} } @inproceedings {1598, title = {Safeguarding Structural Controllability in Cyber-Physical Control Systems}, booktitle = {The 21st European Symposium on Research in Computer Security (ESORICS 2016)}, volume = {9879}, year = {2016}, pages = {471-489}, publisher = {Springer}, organization = {Springer}, address = {Crete, Greece}, abstract = {

Automatic restoration of control wireless networks based on dynamic\ cyber-physical systems has become a hot topic in recent years, since most of their\ elements tend to have serious vulnerabilities that may be exploited by attackers.\ In fact, any exploitation may rapidly extend to the entire control network due to\ its problem of non-locality, where control properties of a system and its structural\ controllability can disintegrate over time. Unfortunately, automated self-healing\ processes may become costly procedures in which the reliability of the strategies\ and the time-critical of any recovery of the control can become key factors to\ re-establish the control properties in due time. This operational need is precisely\ the aim of this paper, in which four reachability-based recovery strategies from\ a thereotical point of view are proposed so as to find the best option/s in terms\ of optimization, robustness and complexity. To do this, new definitions related to\ structural controllability in relation to the type of distribution of the network and\ its control load capacity are given in this paper, resulting in an interesting practical\ study.

}, keywords = {Control systems, cyber-physical systems, restoration, self-healing, structural controllability}, isbn = {978-3-319-45741-3}, author = {Cristina Alcaraz and Javier Lopez} } @inproceedings {430, title = {Recovery of Structural Controllability for Control Systems}, booktitle = {Eighth IFIP WG 11.10 International Conference on Critical Infrastructure Protection, SRI International, Arlington, Virginia, USA }, volume = {441}, year = {2014}, pages = {47-63}, publisher = {Springer}, organization = {Springer}, address = {Arlington, Virginia, USA}, abstract = {

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{\textquoteright}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.\ 

}, keywords = {Control systems, power domination, resilience, structural controllability}, isbn = {978-3-662-45354-4}, issn = {1868-4238}, doi = {http://dx.doi.org/10.1007/978-3-662-45355-1_4}, author = {Cristina Alcaraz and Stephen Wolthusen} }