Utilisation de la corrélation pondérée dans un processus de détection d’intrusions

Generally, an intruder must perform several actions, organized in an intrusion scenario, to achieve his or her malicious objectives. Actions are modeled by their pre and post conditions, which are a set of logical predicates or negations of predicates. Pre conditions of an action correspond to conditions the system’s state must satisfy to perform the action. Post conditions correspond to the effects of executing the action on the system’s state. When an intruder begins his intrusion, we can deduce, from the alerts generated byidss (Intrusion Detection Systems), several possible scenarios, by correlating attacks, that lead to multiple intrusion objectives. However, with no further analysis, we are not able to decide which are the most plausible ones among the possible scenarios. We propose in this paper to define an order over the possible scenarios by weighting the correlation relations between successive attacks composing the scenarios. These weights reflect to what level executing some actions are necessary to execute some action B. We will see that to be satisfactory, the comparison operator between two scenarios must satisfy some properties.     

Conception et réalisation d’un simulateur de canal hertzien

The paper presents the design and implementation of a line-of-sight (Los)microwave channel simulator. The basic principle is to reproduce channel transfer functions given by their amplitude and group delay characteristics by driving a linear transversal filter with precomputed data. The transfer functions can be either collected from measurements in the field or derived from any analytical modelling of the Los microwave channel. It is shown that a thirteen tap filter with a 70 MHz period leads to accurate realtime simulations of selective fading in a 50 MHz bandwidth. The control interface, microprocessorbased, allows an efficient and smooth use of the simulator. Finally,hardware problems and technological solutions related to the implementation are presented.     

Architecture d’un réseau actif à base de services Web

This paper presents a novel active architecture for building and deploying network services:aswa, Web Services based Active network Architecture. At the architectural level,aswa defines an active node whose functionalities are divided into the Node Operating System, the Execution Environment, and the Active Applications. At the implementation level,aswa is a Web Services based platform where new components could be added and deployed, in order to dynamically modify network nodes behavior. Applications can be developed with any language and communicate across heterogeneous environments, and across Internet and Intranet structures. At the deployment levelaswa uses an active node approach, and offers a controlled deployment mode. In terms of security, Authentication of deployed code and protection of the nodes is achieved by the use ofhttps and the header extensions of thesoap envelope. Finally to validate this architecture,aswa defines a Firewall as an Active Application to secure the code deployment.     

CRIM: un module de corrélation d’alertes et de réaction aux attaques

With the growing need for protection of informations systems, the intrusion detection approach is interesting but still imperfect. At the moment two main approaches exist: the behaviour based approach and the scenario detection approach. None of those two approaches is fully satisfactory. They often generate two many false positives and the generated alerts are generally too elementary and imprecise to be efficiently processed by a system administrator. An interesting approach consists in developing a cooperation module to analyze and correlate alerts, to generate a more global and synthetic diagnostic, and help the system administrator to choose the best counter-measure given a detected attack. This article presents the work we have achieved in this context to create theRim module (Cooperation and Recognition of Malevolent Intentions).     

Modélisation d’un anneauSDH pour les besoins de la gestion de fautes

When an anomaly occurs in aSDH network, many notifications are emitted towards the supervision center. The emission of these notifications is the result of the signals treatment on the level of the objects describing the network. This document describes the modeling process of the behavior and the interaction between the objects intervening in the data processing of faults management. It gives a methodology ofSDH network model construction for the needs for faults situations diagnosis.     

Mécanisme de l’évolution des champs électromagnétiques dans un simulateur de grandes dimensions. Projet d’un simulateur semi-rhombique

The purpose of this paper is to evaluate theoretically and experimentally the transient electric field in anemp simulator. Using a time domain analysis, the mechanism of the field deformation can be analysed and consequently modifications can be introduced in the conception of new simulators (for example: rhombic simulator).     

Synthèse optimale d’un réseau de télécommunication avec contraintes de sécurité

A commonly used method for achieving a prescribed security level in a telecommunication network is to manage extra capacities all over the network. This paper describes a number of computational methods, both exact and approximate, for determining a minimum cost network of extra capacities needed to achieve security under any given trunk dimensioning, routing and grouping policy. From a mathematical point of view, it is shown that the problem reduces to the determination of a minimum cost network subject to a number of non simultaneous multicommodity flow requirements. Since real life instances of such problems commonly result in very large linear programs of many thousands of variables and constraints, the techniques of linear programming would be unacceptably time and space-consuming. Instead, it is shown how the use of Lagrangean relaxation in conjunction with sub-gradient optimization schemes can lead to efficient and easy-to-implement solution methods. The various procedures described in this paper form the heart of a general software product for long and medium term planning applications (Supersec program) which has already been used to investigate the economical implications of security requirements in telecommunication networks.     

Correction de deux paquets d’erreurs par un code de Reed-Solomon

Algebraic decoding procedures can be greatly simplified in case the number of errors being corrected is small. The authors present here a decoder which is capable of correcting errors occuring on four bits packets. The considered code is a (15, 11) Reed-Solomon code over GF (16). A Meggitttype decoder has been selected. The hardware implementation consists of 49 ttl (ls) packages and operates for the present at a rate of 5 Mbit/s. The utilisation of this decoding scheme is considered for other Reed-Solomon codes.     

Amélioration de la sensibilité de détection et de la qualité du radargramme d’un radar pénétrant GPR par une modulation micro-onde

The primary effect of the field continuously capted by aGpr is the production of a class which limits the contrast of the reflections on the targets. The target response becomes illegible sight the influence of certain disturbances which are due to the reflections caused by certain parasitic elements which are randomly distributed in the soil and the dispersion phenomenon. We present in this paper an approach based on a μ-wave modulation which allowed stage this problem. The technique suggested makes it possible to do a classification of capted signals. It will be shown that the frequency of modulation f_m must be higher than a cut-off frequency f_c which depends on the electric parameters of the ground. In a second part of this paper, we show how to improve quality of the radargram of a systemGpr by a simple convolution between the collected signal and a wavelet with a defined parameters.     

Réalisation d’un opérateur de traitement numérique rapide par une machine à flux de données

The authors describe a fast, parallel and static data flow architecture that is used for Fast Riccati Operator (Fro)design. This operator has a cellular, regular structure easy to integrate, and is intended to resolve with high speed execution the matrix Riccati equation for filtering purpose. To evaluate its performances, two solving algorithms, Lindquist and quasilinéarisation, are represented and simulated by data flow Petri nets, defined for this purpose. Simulation results are compared to real needs in search and tracking situations.     

L’apprentissage des modes de vie: une base indispensable au développement d’un habitat «intelligent»

The advent of new technologies in the field of data processing, electronics and wireless communications currently support the integration of essential functions for the provision of services tailored to the user needs at home. These services are destined to address two key societal demands, i.e., keeping health costs and energy costs under control. With this objective in mind, a number of research works involving various approaches have been conducted as those carried out atlaas for the purpose of integrating the habits and practices of home automation users. The principles under investigation rely on learning habits. Two examples of application using these concepts are presented through use of two home automation systems for a personalized behavioral monitoring of the elderly with a view to providing home care, and for the automatic management of thermal comfort. Promising results have been obtained and pave the way for efficient and cost effective systems that could be associated with other functions to contribute to the development of a truly «smart home».     

Potentialités des séquences d’étalement chaotiques pour l’amélioration duTEEB d’un systèmeDS-CDMA asynchrone

The use of chaotic sequences as spectral spreading sequences in a Direct Sequence-Code Division Multiple Access is proposed in this paper. The simulation of the system is performed with the system simulator Omnisys. The chaotic spreading sequences are generated from a non-linear recursive equation. The Bit Error Rate of this system is compared with theBER of the same system using binary Gold sequences. The results show that chaotic sequences can improve performances in terms of allowable number of users.     

À propos de la conception de systèmes d’aide aux déplacements des déficients visuels

This paper aims to contribute to studies related to visual handicap in order to reduce/eliminate it with new technologies. It addresses shortly the main principle of 3D world human perception, the main rules for environmental pertinent data acquisition and their processing. The proposed state of art on blind people travel assisting aids (taa) allow to understand the requirements for new aids design. A few examples of research project show how solution from new information technologies (such as artificial vision, virtual reality, high densityvlsi, tactile systems, GPS, wireless networks, etc) can be integrated in new systems. These examples allow also to determine which concepts should be targeted when designing any new travel assistance for blind people autonomous and safe displacement, and to characterise new devices.     

Étude de la génération d’impulsions brèves d’un laser DFB à trois contrôles de phases (3QWS-DFB)

The purpose of this paper is to study the generation of short pulses of the three quarter wave shift distributed feedback (3Qws-dfb) laser by using switching gain technique. We have used the temporal domain model (Tdm) which is a multimode spatio-temporal model that considers simultaneously all the modes of the overall intra-cavity field as well as the two following nonlinear effects, the spectral hole burning (Shb) and the gain saturation. Obtained results showed that a 3Qws-dfb laser can generate short pulses in accordance with Fourier criteria. These results show that 3Qws-dfb lasers are potential candidates as monomode optical sources for long distance high bit rate telecommunications.