Actuation attacks on constrained linear systems: A set-theoretic analysis

Cuenta con un 2º editor: Incluido en el Volumen 53, Issue 2 Article number 145388This paper considers a constrained discrete-time linear system subject to actuation attacks. The attacks are modelled as false data injections to the system, such that the total input (control input plus injection) satisfies hard input constraints. We establish a sufficient condition under which it is not possible to maintain the states of the system within a compact state constraint set for all possible realizations of the actuation attack. The developed condition is a simple function of the spectral radius of the system, the relative sizes of the input and state constraint sets, and the proportion of the input constraint set allowed to the attacker.Ministerio de Economía y Competitividad (España) DPI2017-86918-RJapan Society for the Promotion of Science PE1604

Understanding and mitigating universal adversarial perturbations for computer vision neural networks

Deep neural networks (DNNs) have become the algorithm of choice for many computer vision applications. They are able to achieve human level performance in many computer vision tasks, and enable the automation and large-scale deployment of applications such as object tracking, autonomous vehicles, and medical imaging. However, DNNs expose software applications to systemic vulnerabilities in the form of Universal Adversarial Perturbations (UAPs): input perturbation attacks that can cause DNNs to make classification errors on large sets of inputs. Our aim is to improve the robustness of computer vision DNNs to UAPs without sacrificing the models' predictive performance. To this end, we increase our understanding of these vulnerabilities by investigating the visual structures and patterns commonly appearing in UAPs. We demonstrate the efficacy and pervasiveness of UAPs by showing how Procedural Noise patterns can be used to generate efficient zero-knowledge attacks for different computer vision models and tasks at minimal cost to the attacker. We then evaluate the UAP robustness of various shape and texture-biased models, and found that applying them in ensembles provides marginal improvement to robustness. To mitigate UAP attacks, we develop two novel approaches. First, we propose the Jacobian of DNNs to measure the sensitivity of computer vision DNNs. We derive theoretical bounds and provide empirical evidence that shows how a combination of Jacobian regularisation and ensemble methods allow for increased model robustness against UAPs without degrading the predictive performance of computer vision DNNs. Our results evince a robustness-accuracy trade-off against UAPs that is better than those of models trained in conventional ways. Finally, we design a detection method that analyses the hidden layer activation values to identify a variety of UAP attacks in real-time with low-latency. We show that our work outperforms existing defences under realistic time and computation constraints.Open Acces

The behavioural ecology of green monkeys (Cercopithecus sabaeus) at Mt. Assirik, Senegal

The aims of this study were to provide detailed information on the ecology of green monkeys in Senegal, to examine adaptive behavioural variation by comparing their behaviour with that of other populations of this widespread species-group (C. aethiops), and to use field-data to test hypotheses about adaptive strategies, particularly those concerned with how their foraging patterns changed with the seasonally variable availability and distribution of resources. Field-work was carried out at Mt. Assirik, in the Parc National du Niokolo-Koba, Senegal. The climate, vegetation, and fauna of the region were described. On most criteria, Mt. Assirik is vegetationally richer in density and diversity of species than two study-sites compared in Cameroon, and one in Kenya, where other populations of C. aethiops have been studied. The demographic structure of the population of green monkeys at Mt. Assirik was assessed. The mean size of groups was 19 monkeys, who lived at a comparatively low overall density of 4.4 per km2. This, the lowest density recorded for C. aethiops, is ascribed to the extensive areas of sparse, unsuitable habitat that constitute a large part of the vegetational mosaic of the region.A single group of green monkeys was studied in detail, over one complete annual cycle. Aspects of their feeding, ranging, activity-budgets, and territorial behaviour were recorded during 5-day sample-periods each month, in parallel with close monitoring of the changing composition, density, and distribution of important resources. The green monkeys' diet was omnivorous and diverse, including over 65 species of plants, many invertebrates, and some eggs and meat. Preference was given to fruits and flowers, although particular species were not selected; rather, these foods were eaten in proportion to their availability. Leaves, gum, seeds, and fungi were secondary choice foods. There was little overlap in the composition of the diet from month to month, indicating the strong seasonality of the environment. There was a fairly consistent intake of invertebrates each month. The monkeys spent between 35% and 55% of their time feeding. Diurnal rhythms of activity were strongly influenced by temperature: the monkeys stopped feeding and travelling when it was either too hot or too cold. On a finer time-scale, feeding was more closely synchronized between the monkeys when they fed on less common species. Several age and sex differences in feeding were found. In particular, females with very young infants fed less than other adults. No particular height-niche was occupied by the monkeys. The study group ranged over an area of 1.78 km2, the largest range recorded for any C. aethiops group. Their ranging patterns differed from month to month, and were significantly influenced by the availability and distribution of food, water, sleeping sites, and habitat-types, and by patterns of intergroup relations. Territorial behaviour itself was strongly influenced by the availability and distribution of key food sources, and the intensity of intergroup encounters varied accordingly. Many differences in patterns of feeding and ranging between populations of C. aethiops are related to the floristic composition of the vegetation, but comparisons were limited by lack of appropriate data on the availability and distribution of food at other sites. Data on the seasonally varied patterns of feeding, ranging, and activity-budgets, and changing patterns of resource availability, were drawn together to examine the adaptive strategies underlying the monkeys' behaviour. Several models in optimal foraging theory were tested. Time and energy spent in feeding and travelling increased as food-availability increased. Their choice of diet was optimal in that they were more selective when profitable food-items were common: higher proportions of the diet were given over to fruit and flowers when food-availability was high. In parallel with these strategies, a nutritive balance was maintained by consistent inclusion of at least some foliage and invertebrates in the diet, however much fruit was eaten

Dynamic Model Generation and Classification of Network Attacks

When attempting to read malicious network traffic, security analysts are challenged to determine what attacks are happening in the network at any given time. This need to analyze data and attempt to classify the data requires a large amount of manual time and knowledge to be successful. It can also be difficult for the analysts to determine new attacks if the data is unlike anything they have seen before. Because of the ever-changing nature of cyber-attacks, a need exists for an automated system that can read network traffic and determine the types of attacks present in a network. Many existing works for classification of network attacks exist and contain a very similar fundamental problem. This problem is the need either for labeled data, or batches of data. Real network traffic does not contain labels for attack types and is streaming packet by packet. This work proposes a system that reads in streaming malicious network data and classifies the data into attack models while dynamically generating and reevaluating attack models when needed. This research develops a system that contains three major components. The first is a dynamic Bayesian classifier that utilizes Bayes\u27 Theorem to classify the data into the proper attack models using dynamic priors and novel likelihood functions. The second component is the dynamic model generator. This component utilizes the concept of a cluster validity index to determine the proper time to generate new models. The third component is a model shuffler. This component redistributes misclassified data into attack models that more closely fit the behaviors of the data. Malicious packet captures obtained from two network attack and defense competitions are used to demonstrate the ability of the system to classify data, successfully and reasonably create new attack models, and shuffle the data into more closely related models

User evaluation of the performance of information systems

Information technologies (IT) are considered the primary survival factor for many organizations and the most critical success factor in businesses today. To justify the necessary investment in IT, user evaluation of information systems\u27 performance in organizations is a key consideration. This research investigated a comprehensive and convenient means for end users to assess this performance. Among the existing theories and models on the evaluation of information system performance based on intrinsic technological properties, the Web of System Performance (WOSP) model provides the most comprehensive basis for information system evaluation, and therefore merited further investigation. The research question was how well the eight WOSP performance criteria, namely functionality, usability, flexibility, reliability, security, extendibility, connectivity, and privacy, applied in the context of an individual evaluating one or more information systems for use by an organization. For this, it was important to show that, while these performance criteria were abstract concepts, they can be established and identified clearly, in a manner that is valid in the sense of the meaning and that users would consider important. Illustrative statements for each of the eight criteria were therefore obtained, which users were asked to evaluate. Next, it was necessary to show that users prefer the choice of the eight WOSP criteria to the current dominant instrument for evaluation when evaluating software. This was done using a preference questionnaire where subjects rated both the WOSP model and an alternative means of evaluation along various dimensions, the results being compared by statistical analysis. Finally, it was necessary to show that users rate at least three of the WOSP criteria as being important for evaluating information systems. For this, conjoint analysis was used. A browser was selected as the experimental software for this research. The results showed that users found illustrative statements clear, valid and important for the evaluation of browsers. They also preferred using the WOSP model for the evaluation of browsers over TAM, the current dominant model. Finally, while users attached different levels of importance to the various performance criteria for the selection of browsers, five of the criteria were important to a significant degree

Project Selection in Facility and Infrastructure Maintenance Organizations

The current Air Force Civil Engineer Center (AFCEC) built infrastructure Facility Sustainment Restoration and Modernization (FSRM) portfolio management methodology results in an unbalanced project portfolio. The consequence of this unbalance is that majority of the funding goes towards buildings on the flightline and Facility Support Services activities do not get adequate funding which leads to further deterioration of those facilities. This research investigates whether decision support framework based on Value-Focused Thinking (VFT) process yields better project selection outcomes for facility and infrastructure maintenance organizations. To accomplish that, the investigation focuses on understanding current AFCEC decision support methodology, building an alternative one based on VFT process, and then applying the result to a sampling of projects. Findings of the investigation prove that the VFT process yields a decision support framework that successfully balances FSRM project portfolio by ranking the projects based on their level of contribution to decision-maker’s values affecting facility and infrastructure maintenance organizations

A handbook of wildfire engineering: Guidance for wildfire suppression and resilient urban design

A Handbook of Wildfire Engineering (the Handbook) provides firefighters, engineers and town planners with detailed technical approaches and analysis to enhance the resilience of communities in areas prone to wildfire impacts, and enhance the safety and effectiveness of wildfire suppression at the urban interface during catastrophic wildfire condition

Space use by passerine birds : a study of territory economics in robins Erithacus rubecula and dippers Cinclus cinclus

1. Cost constraints in models of territory size are based on time/activity/laboratory estimates that predict birds using larger territories will incur higher energy costs. The predicted form of the cost constraint may be linear, accelerating or decelerating depending on assumptions inherent in the models. The aim of this study was to assess the reality and form of the cost constraint by making direct measurements of the energy costs of territory use in birds that occupy territories of different size and shape; polygonal territories represented by the robin Erithacus rubecula, and linear by the dipper Cinclus cinclus. Free-living energy expenditure was measured using the doubly-labelled water technique, whilst simultaneously recording patterns of territory use by radio-tracking. 2. Territorial robins concentrated their activity in one or more foraging patches located in bushes. Range polygons containing all the foraging patches used by an individual provided estimates of territory area, and were generally of high eccentricity. A small proportion of robins was classified as non-territorial based on range polygon areas. Furthermore, while territorial robins showed high fidelity to ranges over the short term (days), non-territorial individuals were nomadic. Over the longer term (months), however, some territorial robins showed range drift. Dippers similarly used preferred core regions within ranges, although there was no selection for particular habitat features. 3. Because robins occupied territory polygons which varied from polygonal to highly linear, work was focused on this species to allow intra-specific comparison. Robins tended to commute between foraging patches by flying. It was appropriate, therefore, to describe territories in terms of a number of patches linked by a network of flight paths. This generated two further measures of territory size; the number of patches used and the total flight distance between patches. 4. The robins exploited a renewing food supply. Predictions were tested concerning the temporal scheduling of visits to foraging patches within territories. Patches tended to be separated by flight paths of similar lengths, and were visited in a regular sequence. Although the number of foraging patches used varied, all territories had similar total core areas. Robins using many small foraging patches commuted between patches more often and covered a larger total flight distance during each foraging circuit of the territory. The configurations of foraging patches were used in a highly linear manner. This was true even if the territory containing them was of low eccentricity. 5. Changes in structure and pattern of use varied predictably with territory size, and could be described mathematically. Based on this and published time/activity budgets, a suite of models was developed to predict how energy costs would vary with number of patches used and total flight distance between patches. Models were tested by directly measuring the energy expenditure of robins using different territories. The number of patches used and total flight distance between patches were both significantly correlated with energy expenditure, while territory area was not. One of the models showed a significant fit to the observed data, and suggested that the form of the energy cost constraint on territory size was linear. The effect of territory shape on energy costs was minimal. The implications of these results for models of territory size are discussed. 6. The slope and elevation of the energy cost constraint varied with the morphology of territory occupants. Based on this, an association of morphology with territory size was predicted; robins of lower mass and wing-loading using larger territories. The observed data supported these predictions, and suggested a possible genetic predisposition to particular patterns of territory occupancy in the robin

Application of Reliability and Linear Regression to Enterprise Architecture in Support of the US Air Force\u27s Capability Review and Risk Assessment

This research explored the use of modeling and enterprise architecture in the analysis of Air Force Capabilities. The Air Force accomplishes this through the Capability Review and Risk Assessment (CRRA). The CRRA is currently performed by building architectures which contain Process Sequence Models (PSMs). PSMs are scored by Subject Matter Experts to determine the probability of successfully completing the mission they model and ultimately to determine the risk associated to Air Force capabilities. Two findings were identified. The first is that creating additional architectural viewpoints, some of which are currently being proposed for version 2.0 of the DoD Architecture Framework, can benefit CRRA development. The second is PSMs have fundamental limitations associated with the inability to capture dependencies among activities as well as the inability to get beyond binary success criteria to address issues of capability sufficiency. To remedy these limitations a model called Extended Sequence Models (ESMs) was developed. ESMs extend PSMs by using reliability modeling techniques combined with linear regression to show dependencies between components. This model also allows the effects of capability sufficiency to be captured and related to mission success