Modélisation formelle des systèmes de détection d'intrusions

L’écosystème de la cybersécurité évolue en permanence en termes du nombre, de la diversité, et de la complexité des attaques. De ce fait, les outils de détection deviennent inefficaces face à certaines attaques. On distingue généralement trois types de systèmes de détection d’intrusions : détection par anomalies, détection par signatures et détection hybride. La détection par anomalies est fondée sur la caractérisation du comportement habituel du système, typiquement de manière statistique. Elle permet de détecter des attaques connues ou inconnues, mais génère aussi un très grand nombre de faux positifs. La détection par signatures permet de détecter des attaques connues en définissant des règles qui décrivent le comportement connu d’un attaquant. Cela demande une bonne connaissance du comportement de l’attaquant. La détection hybride repose sur plusieurs méthodes de détection incluant celles sus-citées. Elle présente l’avantage d’être plus précise pendant la détection. Des outils tels que Snort et Zeek offrent des langages de bas niveau pour l’expression de règles de reconnaissance d’attaques. Le nombre d’attaques potentielles étant très grand, ces bases de règles deviennent rapidement difficiles à gérer et à maintenir. De plus, l’expression de règles avec état dit stateful est particulièrement ardue pour reconnaître une séquence d’événements. Dans cette thèse, nous proposons une approche stateful basée sur les diagrammes d’état-transition algébriques (ASTDs) afin d’identifier des attaques complexes. Les ASTDs permettent de représenter de façon graphique et modulaire une spécification, ce qui facilite la maintenance et la compréhension des règles. Nous étendons la notation ASTD avec de nouvelles fonctionnalités pour représenter des attaques complexes. Ensuite, nous spécifions plusieurs attaques avec la notation étendue et exécutons les spécifications obtenues sur des flots d’événements à l’aide d’un interpréteur pour identifier des attaques. Nous évaluons aussi les performances de l’interpréteur avec des outils industriels tels que Snort et Zeek. Puis, nous réalisons un compilateur afin de générer du code exécutable à partir d’une spécification ASTD, capable d’identifier de façon efficiente les séquences d’événements.Abstract : The cybersecurity ecosystem continuously evolves with the number, the diversity, and the complexity of cyber attacks. Generally, we have three types of Intrusion Detection System (IDS) : anomaly-based detection, signature-based detection, and hybrid detection. Anomaly detection is based on the usual behavior description of the system, typically in a static manner. It enables detecting known or unknown attacks but also generating a large number of false positives. Signature based detection enables detecting known attacks by defining rules that describe known attacker’s behavior. It needs a good knowledge of attacker behavior. Hybrid detection relies on several detection methods including the previous ones. It has the advantage of being more precise during detection. Tools like Snort and Zeek offer low level languages to represent rules for detecting attacks. The number of potential attacks being large, these rule bases become quickly hard to manage and maintain. Moreover, the representation of stateful rules to recognize a sequence of events is particularly arduous. In this thesis, we propose a stateful approach based on algebraic state-transition diagrams (ASTDs) to identify complex attacks. ASTDs allow a graphical and modular representation of a specification, that facilitates maintenance and understanding of rules. We extend the ASTD notation with new features to represent complex attacks. Next, we specify several attacks with the extended notation and run the resulting specifications on event streams using an interpreter to identify attacks. We also evaluate the performance of the interpreter with industrial tools such as Snort and Zeek. Then, we build a compiler in order to generate executable code from an ASTD specification, able to efficiently identify sequences of events

Molecular determinants of ligand specificity in carbohydrate-binding modules: an NMR and X-ray crystallography integrated study

Dissertação para obtenção do Grau de Doutor em Bioquímica – Ramo Bioquímica EstruturalThe microbial plant cell wall degradation is one of the most important processes in the global turnover of atmospheric carbon dioxide. The work presented in this thesis addressed the cellulosomes of Clostridium thermocellum and Bacteroides cellulosolvens, essential to the process of cellulose degradation, and aimed to study some of the components involved in their architecture (cohesins and dockerins) and efficiency (Carbohydrate-Binding Modules - CBMs). For this I used a combination of Nuclear Magnetic Resonance (NMR), X-ray crystallography and computer modeling techniques. My objective was to help rationalize the molecular determinants of specificity of CBMs, including the CtCBMs of families 11, 30 and 44, and the mechanisms of molecular recognition between cohesins and dockerins. In Chapter I, I present a general introduction to the theme of degradation of plant cell walls, with special attention to the cellulosome and its components. In Chapter II, I discuss the structural characteristics of the CtCBM11 based on the structures obtained by NMR at 25 and 50 °C and the structure obtained by crystallography. I found that although similar, the structures show some differences, particularly regarding the binding cleft area, which explains the negative results obtained by co-crystallization. In Chapter III and IV I study the molecular determinants of specificity in modules CtCBM11, 30 and 44, based on NMR and computer modeling data. I found that the atoms of the cellooligosaccharides most important for binding are the ones at positions 2 and 6 of the central units of the ligands. Moreover, I characterized the mechanisms responsible for selection and binding of these modules to various substrates. I established that binding occurs by a mechanism for conformational selection, where the topology of the residues of the protein, the conformation of the ligand and the number of glucose units, play a fundamental role. Chapters V and VI reveal the determination of the 3D structure of the cohesin-module X-dockerin complex of C. thermocellum and the cohesin-dockerin complex of B. cellulosolvens, respectively. Both complexes belong to the type II and their analysis allowed obtaining important information about the structural features that define the cohesin-dockerin interaction. The structure belonging to C. thermocellum revealed that the module X is essential for the stability of the complex. Moreover, for the first time the 3D structure of a cohesin-dockerin complex from B. cellulosolvens was determined. In this complex the dockerin is rotated 180º when compared to other complexes. This gives the cellulosome plasticity. In the final chapters, I present the NMR and X-ray crystallography techniques I used throughout the study. Finally, I draw some general conclusions about all the work done.Fundação para a Ciência e Tecnologia - SFRH/BD/35992/2007, and projects PTDC/QUI/68286/2006, PTDC/QUI-BIQ/100359/2008 and PTDC/BIA-PRO/103980/200

Construct Validation Of A Learning & Talent Development Strategic Alignment Scale

The purpose of a Learning & Talent Development (LTD) function in organizations is to develop workforce capabilities to execute strategic priorities. A strategically aligned LTD function is perceived as a business partner and as an asset to the business. The study design followed a psychometrically validated scale development process with the goal of confirming a valid and reliable measure of strategic alignment in LTD functions. Three studies were performed to (1) generate and test the initial pool of items, (2) explore the factor structure, and (3) confirm the factor structure. The results of three studies produced a two-factor, 15-item factor structure for the LSDA scale with 58.143% total variance explained. The results of the study describe the type of relationship internal customers require to perceive the LTD function as aligned to the business and also addresses how LTD members that have a desire to be strategically aligned can proactively design and manage the relationship to gain cooperative work environments in which LTD can exercise its role in creating and modeling alignment

Un processus formel d'intégration de politiques de contrôle d'accès dans les systèmes d'information

Security is a key aspect in information systems (IS) development. One cannot build a bank IS without security in mind. In medical IS, security is one of the most important features of the software. Access control is one of many security aspects of an IS. It defines permitted or forbidden execution of system's actions by an user. Between the conception of an access control policy and its effective deployment on an IS, several steps can introduce unacceptable errors. Using formal methods may be an answer to reduce errors during the modeling of access control policies. Using the process algebra EB[superscript 3], one can formally model IS. Its extension, EB[superscript 3]SEC, was created in order to model access control policies. The ASTD notation combines Harel's Statecharts and EB[superscript 3] operators into a graphical and formal notation that can be used in order to model IS. However, both methods lack tools allowing a designer to prove or verify security properties in order to validate an access control policy. Furthermore, the implementation of an access control policy must correspond to its abstract specification. This thesis defines translation rules from EB[superscript 3] to ASTD, from ASTD to Event-B and from ASTD to B. It also introduces a formal architecture expressed using the B notation in order to enforce a policy over an IS. This modeling of access control policies in B can be used in order to prove properties, thanks to the B prover, but also to verify properties using ProB, a model checker for B. Finally, a refinement strategy for the access control policy into an implementation is proposed. B refinements are proved, this ensures that the implementation corresponds to the initial model of the access control policy

Ny metodikk for kobling av mesoskala og stasjonære CFD modeller for vindressurskartlegging

The estimation of the energy production of wind farms is a key factor for the development of wind energy projects. Currently, these estimations utilize only a few onsite measurement points to estimate the wind resource at the location of the wind turbines by means of a wind flow model. One of the most advanced wind flow models utilized in the wind energy industry for this purpose are the steady-state computational fluid dynamic (CFD) models. These models have proven to be successful in modelling the wind flow in complex terrain. Nevertheless, there are some limitations in their applicability at sites with complex weather patterns. In this PhD thesis, these limitations are addressed by coupling a CFD model with a mesoscale meteorological model (MMM). MMMs are widely used for weather forecast and can reproduce the complex weather phenomena that a CFD model lacks. In this study, the framework to couple both models consists in utilizing the mesoscale simulation results to compute the boundary conditions of the CFD model. Two variants of the meso-microscale coupling approach are here studied. The first approach consists in utilizing the average values of the mesoscale fields by wind directional sector. It is shown that this approach improves the wind estimations in complex terrain and in areas that are located at the wake of the terrain features of a site. Nevertheless, the approach presents important limitations in sites where the wind blows from few wind directions. The second approach addresses this limitation by extracting weather patterns from the mesoscale simulations by means of a fully automated clustering methodology. This classification technique is capable of extracting the predominant weather patterns and organizing them in a meaningful way. Overall, by downscaling the extracted patterns the modelling error is reduced compared with the mesoscale model. Such a methodology has a lot of potential for wind turbine wake studies as well as for forecasting solutions that utilize CFD models

Integrating formal methods into medical software development : the ASM approach

Medical devices are safety-critical systems since their malfunctions can seriously compromise human safety. Correct operation of a medical device depends upon the controlling software, whose development should adhere to certification standards. However, these standards provide general descriptions of common software engineering activities without any indication regarding particular methods and techniques to assure safety and reliability. This paper discusses how to integrate the use of a formal approach into the current normative for the medical software development. The rigorous process is based on the Abstract State Machine (ASM) formal method, its refinement principle, and model analysis approaches the method supports. The hemodialysis machine case study is used to show how the ASM-based design process covers most of the engineering activities required by the related standards, and provides rigorous approaches for medical software validation and verification

Conference methods training in American business and industry

Thesis (M.A.)--University of Kansas, Speech Communication and Human Relations, 1973

Toward an Integrative Understanding of Information Technology Training Research across Information Systems and Human-Computer Interaction: A Comprehensive Review

Researchers investigating issues in the domain of training and human-computer interaction share a common interest in ensuring that users are skilled in the use of Information Technologies (IT). When users have the necessary skills, they can utilize IT productively and also have a pleasant human-to-computer interaction. Over the past three decades, Information System (IS) researchers have made considerable efforts in identifying the most effective ways to develop users’ IT skills. However, at this point in time, there are many changes taking place in the IT environment and organizations find it challenging to keep their employees trained and updated on IT skills. Hence, it is important for the IS community to respond by taking the lead in identifying and conducting research that can help organizations effectively address these challenges. We take the first step in conducting a comprehensive review of training research published in major IS and HCI journals over the past three decades so as to synthesize IT training research, provide an integrative understanding of findings, and propose directions for future research. Our study indicates that while IS research on training has made steady progress in advancing our understanding of alternative IT training methods and cognitive learning processes, it also has several shortcomings. Past research has: a) focused primarily on the training program without sufficient attention to activities prior to and after the program, b) used a small set of theoretical foundations, and c) focused on a few topics and on single-user systems rather than integrated enterprise systems. Critical issues such as improving user motivations prior to training, transfer of training skills to the workplace, assessment of training, and supporting user learning that occurs after training have not been given adequate attention. We identify several research opportunities by tapping into relatively unexplored theories and urge researchers to continue research to address the gaps identified in this comprehensive review as well as to develop innovative methods to help employees learn through newer channels, such as e-learning and social media