Classical reliability theory usually deals with internal system failures and considers providing redundancy and improving reliability (availability) of elements as measures of improving system reliability (availability). When systems are exposed to external threats one faces the problem of system survivability enhancement and applies measures that may be ineffective from the reliability point of view but reduce the system vulnerability (example of such measures is separation of system elements). In the case of unintentional external impacts determining risk reduction strategies usually assumes a static external threat, however the September 11, 2001 attack illustrated that major threats today involve strategic attackers. There is a need to proceed beyond earlier research and assume that both the defender and attacker of a system are fully strategic optimizing agents. When considering the risk of intentional attacks, it is important to realize that the use of an adaptive strategy allows attacker to target the most sensitive parts of a system. Choosing the time, place, and means of attacks gives the attacker an advantage over the defender. On the other hand the defensive strategy can include actions (such as camouflage, concealment and decoys) that cannot protect the system against unintentional impacts, but become effective against strategic attackers. The optimal system defense policy presumes allocating available resources among possible defensive investments taking into account the attacker's strategy that can be adapted and optimized for any defense alternative.
The emerging discipline of system survivability and defense requires joint effort of researchers dealing with statistical analysis, operations research, reliability engineering and game theory. This special issue contains papers representing just several aspects of this wide field. The paper "On some models of acceptable risk" by M. Finkelstein discusses classification of possible system losses via a stochastic comparison based on Cdf of acceptable loss. This approach helps to determine acceptable, unacceptable and intermediate regions for the level of loss.
The paper "Strategic defense and attack of complex networks" by K. Hausken considers influence of system structure (configuration of reliability block diagram) on optimal strategy of distribution of defender's and attacker's investments among the elements composing the system.
The paper "Secrecy in defensive allocations as a strategy for achieving more cost-effective attacker deterrence" by N. S. Dighe, J. Zhuang and V. M. Bier considers strategy for achieving cost-effective attack deterrence by allocating the defensive resource in the system consisting of two elements under assumption that the attacker cannot reveal the resource distribution.
The paper "Optimal distribution of constrained resources in bi-contest detection-impact game" by G. Levitin analyses the optimal distribution of constrained attacker and defender resources between target detection (camouflage) and target destruction (protection) efforts.
The paper "Rebound wall: a novel technology against DoS attacks" by Y. Dai, X. Li, X. Zou and B. Xiao presents a novel and robust mechanism for protecting network servers from intentional Denial of Service attacks and analyzes its efficiency.
The paper "Application of advanced computational techniques to the vulnerability assessment of network systems exposed to uncertain harmful events" by Claudio M. Rocco, Daniel E. Salazar and Enrico Zio presents an application of advanced computational techniques for analyzing the propagation of attacks in complex interconnected networks and for evaluating the network vulnerability.
The paper "Assessing resource requirements for maritime domain awareness and protection (security)" by D. P. Gaver, P. A. Jacobs and H. Sato presents a model for evaluating the probability that a hostile vessel entering a maritime domain is successfully neutralized before reaching its destination given that non-hostile vessels can be misclassified by defender's sensors.
I would like to thank all the authors, first for contributing to the issue, and then for putting up with demands for revision. I am immensely grateful to the authors for their patience and their perseverance in helping to achieve the high standards of the papers. We would have never achieved our goals without the assistance of the following reviewers: Prof. George E. Apostolakis (Massachusetts Institute of Technology, USA), Dr. Ji Hwan Cha (Pukyong National University, Korea), Dr. Lucia Cloth (University of Twente, The Netherlands), Prof. Maxim Finkelstein (University of the Free State, South Africa), Dr. Seth Guikema (Johns Hopkins University, USA), Prof. Henrik Johansson (Lund University, Sweden), Dr. Xiaolin (Andy) Li (Oklahoma State University, USA), Dr. Dmitri Nizovtsev (Washburn University, USA), Prof. Jan M. van Noortwijk (Delft University of Technology, The Netherlands), Prof. Markus Siegle (University of the Federal Armed Forces, Germany), Prof. Lev V. Utkin (St.Petersburg Forest Technical Academy, Russia), Dr. Jun Zhuang (University of Wisconsin-Madison, USA).
Last but not the least, I thank Prof. Krishna B. Misra, Editor-in-Chief of the International Journal of Performability Engineering, for enthusiastically supporting me in this endeavor.
Gregory Levitin received the BS and MS degrees in Electrical Engineering from Kharkov Politechnic Institute (Ukraine) in 1982, the BS degree in Mathematics from Kharkov State University in 1986 and PhD degree in Industrial Automation from Moscow Research Institute of Metalworking Machines in 1989. From 1982 to 1990 he worked as software engineer and researcher in the field of industrial automation. From 1991 to 1993 he worked at the Technion (Israel Institute of Technology) as a postdoctoral fellow at the faculty of Industrial Engineering and Management. Dr.Levitin is presently a senior expert at the Reliability Department of the Israel Electric Corporation and adjunct senior lecturer at the Technion. His current interests are in operations research and artificial intelligence applications in reliability and power engineering. In this field Dr. Levitin has published more than 120 papers and four books. He is senior member of IEEE and chair of the ESRA Technical Committee on System Reliability. He serves in editorial boards of IEEE Transactions on Reliability, Reliability Engineering and System Safety and International Journal of Performability Engineering.