On the robustness of network infrastructures to disasters and physical attacks

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (p. 153-158).Networks are vulnerable to natural disasters, such as earthquakes or floods, as well as to physical attacks, such as an Electromagnetic Pulse (EMP) attack. Such realworld events happen in specific geographical locations and disrupt specific parts of the network. Therefore, the geographical layout of the network determines the impact of such events on the network's connectivity. We focus on network analysis and design under a geographic failure model of (geographical) networks to such disasters. Initially, we aim to identify the most vulnerable parts of data networks to attack. That is, the locations of a disaster that would have the maximum disruptive effect on a network in terms of capacity and connectivity. We consider graph models in which nodes and links are geographically located on a plane, and model the disaster event as a line segment or circular disk. We develop polynomial time algorithms for finding the worst possible cut in this setting. Then, we obtain numerical results for a specific backbone network, thereby demonstrating the applicability of our algorithms to real-world networks. We also develop tools to calculate network metrics after a 'random' geographic disaster. The random location of the disaster allows us to model situations where the physical failures are not targeted attacks. In particular, we consider disasters that take the form of a 'random' circular disk or line in a plane. Using results from geometric probability, we are able to calculate some network performance metrics to such a disaster in polynomial time. In particular, we can evaluate average two-terminal reliability in polynomial time under these 'random' cuts. This is in contrast to the case of independent link failures for which there exists no known polynomial time algorithm to calculate this reliability metric. We present some numerical results to show the significance of geometry on the survivability of the network. This motivates the formulation of several network design problems in the context of randomly located disasters. We also study some min-cut and max-flow problems in a geographical setting. Specifically, we consider the problem of finding the minimum number of failures, modeled as circular disks, to disconnect a pair of nodes and the maximum number of failure disjoint paths between a pair of nodes. This model applies to the scenario where an adversary is attacking the network multiple times with intention to reduce its connectivity. We present a polynomial time algorithm to solve the geographic mincut problem and develop an ILP formulation, an exact algorithm, and a heuristic algorithm for the geographic max-flow problem. Finally, we study the reliability of power transmission networks under regional disasters. Initially, we quantify the effect of large-scale non-targeted disasters and their resulting cascade effects on power networks. We then model the dependence of data networks on the power systems and consider network reliability in this dependent network setting. Our novel approach provides a promising new direction for modeling and designing networks to lessen the effects of geographical disasters or attacks.by Sebastian James Neumayer.Ph.D

Forensic Memory Analysis for Apple OS X

Analysis of raw memory dumps has become a critical capability in digital forensics because it gives insight into the state of a system that cannot be fully represented through traditional disk analysis. Interest in memory forensics has grown steadily in recent years, with a focus on the Microsoft Windows operating systems. However, similar capabilities for Linux and Apple OS X have lagged by comparison. The volafox open source project has begun work on structured memory analysis for OS X. The tool currently supports a limited set of kernel structures to parse hardware information, system build number, process listing, loaded kernel modules, syscall table, and socket connections. This research addresses one memory analysis deficiency on OS X by introducing a new volafox module for parsing file handles. When open files are mapped to a process, an examiner can learn which resources the process is accessing on disk. This listing is useful for determining what information may have been the target for exfilitration or modification on a compromised system. Comparing output of the developed module and the UNIX lsof (list open files) command on two version of OS X and two kernel architectures validates the methodology used to extract file handle information

LIPIcs, Volume 274, ESA 2023, Complete Volume

LIPIcs, Volume 274, ESA 2023, Complete Volum

Combinatorial Optimization

This report summarizes the meeting on Combinatorial Optimization where new and promising developments in the field were discussed. Th

Molecular Similarity and Xenobiotic Metabolism

MetaPrint2D, a new software tool implementing a data-mining approach for predicting sites of xenobiotic metabolism has been developed. The algorithm is based on a statistical analysis of the occurrences of atom centred circular fingerprints in both substrates and metabolites. This approach has undergone extensive evaluation and been shown to be of comparable accuracy to current best-in-class tools, but is able to make much faster predictions, for the first time enabling chemists to explore the effects of structural modifications on a compound’s metabolism in a highly responsive and interactive manner.MetaPrint2D is able to assign a confidence score to the predictions it generates, based on the availability of relevant data and the degree to which a compound is modelled by the algorithm.In the course of the evaluation of MetaPrint2D a novel metric for assessing the performance of site of metabolism predictions has been introduced. This overcomes the bias introduced by molecule size and the number of sites of metabolism inherent to the most commonly reported metrics used to evaluate site of metabolism predictions.This data mining approach to site of metabolism prediction has been augmented by a set of reaction type definitions to produce MetaPrint2D-React, enabling prediction of the types of transformations a compound is likely to undergo and the metabolites that are formed. This approach has been evaluated against both historical data and metabolic schemes reported in a number of recently published studies. Results suggest that the ability of this method to predict metabolic transformations is highly dependent on the relevance of the training set data to the query compounds.MetaPrint2D has been released as an open source software library, and both MetaPrint2D and MetaPrint2D-React are available for chemists to use through the Unilever Centre for Molecular Science Informatics website.----Boehringer-Ingelhie

LIPIcs, Volume 244, ESA 2022, Complete Volume

LIPIcs, Volume 244, ESA 2022, Complete Volum

Robust services in dynamic systems

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.Includes bibliographical references (p. 191-202).Our growing reliance on online services accessible on the Internet demands highly- available systems that work correctly without interruption. This thesis extends previous work on Byzantine-fault-tolerant replication to meet the new requirements of current Internet services: scalability and the ability to reconfigure the service automatically in the presence of a changing system membership. Our solution addresses two important problems that appear in dynamic replicated services: First, we present a membership service that provides servers and clients in the system with a sequence of consistent views of the system membership (i.e., the set of currently available servers). The membership service is designed to be scalable, and to handle membership changes mostly automatically. Furthermore, the membership service is itself reconfigurable, and tolerates arbitrary faults of a subset of the servers that are implementing it at any instant. The second part of our solution is a generic methodology for transforming replicated services that assume a fixed membership into services that support a dynamic system membership. The methodology uses the output from the membership service to decide when to reconfigure.(cont.) We built two example services using this methodology: a dynamic Byzantine quorum system that supports read and write operations, and a dynamic Byzantine state machine replication system that supports any deterministic service. The final contribution of this thesis is an analytic study that points out an obstacle to the deployment of replicated services based on a dynamic membership. The basic problem is that maintaining redundancy levels for the service state as servers join and leave the system is costly in terms of network bandwidth. To evaluate how dynamic the system membership can be, we developed a model for the cost of state maintenance in dynamic replicated services, and we use measured values from real-world traces to determine possible values for the parameters of the model. We conclude that certain deployments (like a volunteer-based system) are incompatible with the goals of large- scale reliable services. We implemented the membership service and the two example services. Our performance results show that the membership service is scalable, and our replicated services perform well, even during reconfigurations.by Rodrigo Seromenho Miragaia Rodrigues.Ph.D