Submitted by Valquíria Barbieri (kikibarbi@hotmail.com) on 2018-04-20T20:41:24Z No. of bitstreams: 1 DISS_2015_Thaianny Rodrigues de Souza.pdf: 1062092 bytes, checksum: 273aadc537dd50322a56ee59af815ad9 (MD5) / Approved for entry into archive by Jordan (jordanbiblio@gmail.com) on 2018-05-03T17:51:30Z (GMT) No. of bitstreams: 1 DISS_2015_Thaianny Rodrigues de Souza.pdf: 1062092 bytes, checksum: 273aadc537dd50322a56ee59af815ad9 (MD5) / Made available in DSpace on 2018-05-03T17:51:30Z (GMT). No. of bitstreams: 1 DISS_2015_Thaianny Rodrigues de Souza.pdf: 1062092 bytes, checksum: 273aadc537dd50322a56ee59af815ad9 (MD5) Previous issue date: 2015-02-19 / Para o sucesso de programas de melhoramento é necessário um bom material genético disponível, fatores ambientais favoráveis e métodos de seleção adequados aos objetivos do programa. Neste contexto, o presente estudo objetivou avaliar a variabilidade genética existente, bem como métodos de seleção adequados para uma população de Eucalyptus camaldulensis em teste de progênie. O Eucalyptus camaldulensis Dehnh é uma espécie que se destaca no gênero Eucalyptus, com ampla plasticidade, adaptabilidade e usos múltiplos. O experimento está instalado no município de Santo Antônio do Leverger – MT, contendo 117 progênies, em experimento conduzido em blocos ao acaso. Os resultados obtidos através dos parâmetros genéticos indicaram herdabilidade individual e média de progênies de média magnitude para os caracteres DAP e FF e de baixa magnitude para ALTT, ALTC e SOB. indicando certo controle genético. Detectou-se variabilidade genética para os caracteres analisados na população de Eucalyptus camaldulensis, com possibilidades de ganhos genéticos na sequência do programa de melhoramento genético. A seleção entre e dentro de progênies bem como a seleção combinada, indicam a possibilidade de ganhos genéticos, no entanto a seleção individual permitiu maximizar os ganhos mediante seleção para os caracteres estudados. / For the success of enhancements programs it`s necessary a good genetic material available, favorable environmental factors and selection methods appropriate to the program objectives. In this context, this study aimed to evaluate the current genetic variability as well as suitable screening methods for a population of Eucalyptus camaldulensis in progeny test. Eucalyptus camaldulensis Dehnh is a species that stands out in the Eucalyptus genus, with extensive plasticity, adaptability and multiple use. The experiment is installed at the Santo Antônio de Leveger county in the Brazilian state of Mato Grosso - containing 117 progenies, in a randomized blocks conducted experiment. The results obtained through genetic parameters indicated individual heritability and average magnitude of average progenies for DAP characters and FF and low magnitude to ALTT, ALTC and SOB. indicating some genetic control. It was detected genetic variability for the traits analyzed in the population of Eucalyptus camaldulensis with possibilities of genetic gains following the enhancement program. The selection among and within families and the combined screening, indicate the possibility of genetic gains, however individual screening allowed maximize gains for the studied characters.

Les entrepôts de données permettent le stockage et la consolidation, en une seule localité, d'une quantité gigantesque d'information pour être interrogée par des requêtes décisionnelles complexes dites requêtes de jointures en étoiles. Afin d'optimiser ses requêtes, plusieurs travaux emploient des techniques d'optimisations comme les index de jointure binaires et la fragmentation horizontale durant la phase de conception physique d'un entrepôt de données. Cependant, ces travaux proposent des algorithmes statiques qui sélectionnent ces techniques de manière isolée et s'intéressent à l'optimisation d'un seul objectif à savoir les performances des requêtes. Notre principale contribution dans cette thèse est de proposer une nouvelle vision de sélection des techniques d'optimisation. Notre première contribution est une sélection incrémentale qui permet de mettre à jour de manière continuelle le schéma d'optimisation implémenté sur l'ED, ce qui assure l'optimisation continuelle des requêtes décisionnelles. Notre seconde contribution est une sélection incrémentale jointe qui combine deux techniques d'optimisation pour couvrir l'optimisation d'un maximum de requêtes et respecter au mieux les contraintes d'optimisation liées à chacune de ces techniques. A l'issu de ces propositions, nous avons constaté que la sélection incrémentale engendre un coût de maintenance de l'ED. Ainsi, notre troisième proposition est une formulation et r!:solution du problème multi-objectif de sélection des techniques d'optimisation où il faut optimiser deux objectifs: la performance des requêtes et le coût de maintenance de l'ED. / Data Warehouses store into a single location a huge amount of data. They are interrogated by complex decisional queries called star join queries. To optimize such queries, several works propose algorithms for selecting optimization techniques such as Binary Join Indexes and Horizontal Partitioning during the DW physical design. However, these works propose static algorithms, select optimization techniques in and isolated way and focus on optimizing a single objective which is the query performance. Our main contribution in this thesis is to propose a new vision of optimization techniques selection. Our first contribution is an incremental selection that updates continuously the optimization scheme implemented on the DW, to ensure the continual optimization of queries. To deal with queries complexity increase, our second contribution is a join incremental selection of two optimization techniques which covers the optimization of a maximum number or queries and respects the optimization constraints. Finally, we note that the incremental selection generates a maintenance cost to update the optimization schemes. Thus, our third prop05ilion is to formulate and resolve a multi-objective selection problem or optimization techniques where we have two objectives to optimize : queries performance and maintenance cost of the DW.

Current Security Information and Event Management systems (SIEMs) constitute the central platform of modern security operating centers. They gather events from various sensors (intrusion detection systems, anti-virus, firewalls, etc.), correlate these events, and deliver synthetic views for threat handling and security reporting. Research in SIEM technologies has traditionally focused on providing a comprehensive interpretation of threats, in particular to evaluate their importance and prioritize responses accordingly. However, in many cases, threat responses still require humans to carry out the analysis and decision tasks e.g., understanding the threats, defining the appropriate countermeasures and deploying them. This is a slow and costly process, requiring a high level of expertise, and remaining error-prone nonetheless. Thus, recent research in SIEM technology has focused on the ability to automate the process of selecting and deploying countermeasures. Several authors have proposed automatic response mechanisms, such as the adaptation of security policies, to overcome the limitations of static or manual response. Although these approaches improve the reaction process (making it faster and/or more efficient), they remain limited since these solutions do not analyze the impact of the countermeasures selected to mitigate the attacks. In this thesis, we propose a novel and systematic process to select the optimal countermeasure from a pool of candidates, by ranking them based on a trade-off between their efficiency in stopping the attack and their ability to preserve, at the same time, the best service to normal users. In addition, we propose a model to represent graphically attacks and countermeasures, so as to determine the volume of each element in a scenario of multiple attacks. The coordinates of each element are derived from a URI. This latter is mainly composed of three axes: user, channel, and resource. We use the CARVER methodology to give an appropriate weight to each element composing the axes in our coordinate system. This approach allows us to connect the volumes with the risks (i.e. big volumes are equivalent to high risk, whereas small volumes are equivalent to low risk). Two concepts are considered while comparing two or more risk volumes: Residual risk, which results when the risk volume is higher than the countermeasure volume; and Collateral damage, which results when the countermeasure volume is higher than the risk volume. As a result, we are able to evaluate countermeasures for single and multiple attack scenarios, making it possible to select the countermeasure or group of countermeasures that provides the highest benefit to the organization

Made available in DSpace on 2015-03-26T13:40:07Z (GMT). No. of bitstreams: 1 texto completo.pdf: 372745 bytes, checksum: 6f1e60efc5a019ffb5aabeff2579b6ad (MD5) Previous issue date: 2007-07-13 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The objective of this work was to select superior genotypes of the yellow passion flower related to productivity and quality of the fruits. A population of 26 families of whole brothers was evaluated in the second year of production, in a design of random plots, with three repetitions, starting with four plants per plot. The experiment was carried out in the experimental area of Fruitculture in the Departamento de Fitotecnia of the Universidade Federal de Viçosa, in Viçosa, Minas Gerais State, Brazil. In the selection among and within the families, the efficiency of the direct and indirect selection as well as that based on the classical index was verified. The selection strategies among and within, combined, massal and stratified massal were compared. The results found by the selection among and within were compared with those obtained from the selection made in this same population in the first year of production. The characteristics measured were number of fruits per plant, estimated production per plant, length of the fruit, diameter of the fruit, weight of the fruit, weight of the peel, thickness of the peel, weight of the pulp, color of the pulp, percentage of the pulp, total content of soluble solids, titrable total acidity and the rate between the total soluble solids/titrable total acidity. Samples of 10 fruits of each plant were obtained to evaluate the qualitative characteristics of the fruits. The collection of the fruits for the analyses was made as they became yellowishgreen, during the second year of production, from January to July 2006. All the statistical analyses were made with the genetics and statistics software GENES. The selection gains were estimated based on a percentage of 24% among families and of 25% within families for all the characteristics measured. The selection criterium adopted for all the characteristics was the increase in peel their original mediuns, except for the weight and thickness of the peel for which a decrease was desired. For the characteristics choice that were part of the classic index of selection, the multicolinearity diagnosis was carried out, using the autovalues and the autovectors analyses. The selected characteristics to make up the index were estimated production per plant, diameter of the fruit, pulp percentage, pulp color and total titrable acidity. The use of the strategy of simultaneous selection of characters, based on the classic index showed estimations of gains greater than those of the other methodologies, in estimated production per plant and pulp percentage. In the direct selection, the estimations of gains were greater in pulp color and total titrable acidity. The combined selection, when compared to the among and within selection massal and stratified massal, provided the greatest estimations of gains in 11 out of 13 characteristics evaluated, except length and weight of the fruit, thus being the most suitable strategy for the breeding of the population studied. The evaluations made in the first year of production generated satisfactory results, which practically were reproduced in the second year, and therefore can be recommended, because of costs and time reduction of the selection cycle. / Com o objetivo de selecionar genótipos de maracujazeiro amarelo superiores quanto à produtividade e qualidade dos frutos, uma população constituída de 26 famílias de irmãos completos foi avaliada no segundo ano de produção, em delineamento de blocos casualizados, com três repetições e originalmente com quatro plantas por parcela. O trabalho foi realizado na área experimental de Fruticultura do Departamento de Fitotecnia da Universidade Federal de Viçosa, em Viçosa, MG. Verificou-se, na seleção entre e dentro de famílias, a eficiência da seleção direta, indireta e com base em índice clássico. Compararam-se as estratégias de seleção entre e dentro, combinada, massal e massal estratificada. Os resultados encontrados pela seleção entre e dentro foram confrontados com os obtidos em seleção realizada, nessa mesma população, no primeiro ano de produção. As características mensuradas foram número de frutos por planta, produção estimada por planta, comprimento do fruto, diâmetro do fruto, massa do fruto, massa da casca, espessura da casca, massa da polpa, coloração da polpa, porcentagem de polpa, teor de sólidos solúveis totais, acidez total titulável e relação entre teor de sólidos solúveis totais/acidez total titulável. Foi obtida amostra de 10 frutos de cada planta, para avaliação das características qualitativas dos frutos. A colheita dos frutos foi feita de forma parcelada durante o segundo ano de produção, de janeiro a julho de 2006. Os frutos destinados à análise foram colhidos a partir do estádio verde-amarelo . Todas as análises estatísticas foram realizadas com o aplicativo computacional em genética e estatística (GENES). Foram estimados os ganhos de seleção em função de uma porcentagem de seleção de 24% entre famílias e 25% dentro de famílias para todas as características mensuradas. O critério de seleção adotado para todas as características foi o acréscimo em suas médias originais, exceto em massa e espessura da casca, em que se buscou o decréscimo. Para escolha das características que fizeram parte do índice clássico de seleção, foi realizado o diagnóstico de multicolinearidade, empregando para isso a análise dos autovalores e autovetores. As características selecionadas para compor o índice foram produção estimada por planta, diâmetro do fruto, porcentagem de polpa, coloração da polpa e acidez total titulável. A utilização da estratégia de seleção simultânea de caracteres, com base no índice clássico apresentou estimativas de ganhos superiores às das outras metodologias em produção estimada por planta e porcentagem de polpa. Na seleção direta, as estimativas de ganhos foram superiores em coloração de polpa e acidez total titulável. A seleção combinada, quando comparada à seleção entre e dentro, massal e massal estratificada, proporcionou as maiores estimativas de ganhos em 11 das 13 características avaliadas, exceto comprimento e massa do fruto, sendo, assim, a estratégia mais apropriada para o melhoramento genético da população estudada. A realização das avaliações no primeiro ano de produção gera resultados satisfatórios, os quais praticamente, se reproduzem no segundo ano, podendo ser recomendada, por reduzir o custo e o tempo de realização do ciclo de seleção.

Made available in DSpace on 2015-03-26T13:40:07Z (GMT). No. of bitstreams: 1 texto completo.pdf: 372745 bytes, checksum: 6f1e60efc5a019ffb5aabeff2579b6ad (MD5) Previous issue date: 2007-07-13 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The objective of this work was to select superior genotypes of the yellow passion flower related to productivity and quality of the fruits. A population of 26 families of whole brothers was evaluated in the second year of production, in a design of random plots, with three repetitions, starting with four plants per plot. The experiment was carried out in the experimental area of Fruitculture in the Departamento de Fitotecnia of the Universidade Federal de Viçosa, in Viçosa, Minas Gerais State, Brazil. In the selection among and within the families, the efficiency of the direct and indirect selection as well as that based on the classical index was verified. The selection strategies among and within, combined, massal and stratified massal were compared. The results found by the selection among and within were compared with those obtained from the selection made in this same population in the first year of production. The characteristics measured were number of fruits per plant, estimated production per plant, length of the fruit, diameter of the fruit, weight of the fruit, weight of the peel, thickness of the peel, weight of the pulp, color of the pulp, percentage of the pulp, total content of soluble solids, titrable total acidity and the rate between the total soluble solids/titrable total acidity. Samples of 10 fruits of each plant were obtained to evaluate the qualitative characteristics of the fruits. The collection of the fruits for the analyses was made as they became yellowishgreen, during the second year of production, from January to July 2006. All the statistical analyses were made with the genetics and statistics software GENES. The selection gains were estimated based on a percentage of 24% among families and of 25% within families for all the characteristics measured. The selection criterium adopted for all the characteristics was the increase in peel their original mediuns, except for the weight and thickness of the peel for which a decrease was desired. For the characteristics choice that were part of the classic index of selection, the multicolinearity diagnosis was carried out, using the autovalues and the autovectors analyses. The selected characteristics to make up the index were estimated production per plant, diameter of the fruit, pulp percentage, pulp color and total titrable acidity. The use of the strategy of simultaneous selection of characters, based on the classic index showed estimations of gains greater than those of the other methodologies, in estimated production per plant and pulp percentage. In the direct selection, the estimations of gains were greater in pulp color and total titrable acidity. The combined selection, when compared to the among and within selection massal and stratified massal, provided the greatest estimations of gains in 11 out of 13 characteristics evaluated, except length and weight of the fruit, thus being the most suitable strategy for the breeding of the population studied. The evaluations made in the first year of production generated satisfactory results, which practically were reproduced in the second year, and therefore can be recommended, because of costs and time reduction of the selection cycle. / Com o objetivo de selecionar genótipos de maracujazeiro amarelo superiores quanto à produtividade e qualidade dos frutos, uma população constituída de 26 famílias de irmãos completos foi avaliada no segundo ano de produção, em delineamento de blocos casualizados, com três repetições e originalmente com quatro plantas por parcela. O trabalho foi realizado na área experimental de Fruticultura do Departamento de Fitotecnia da Universidade Federal de Viçosa, em Viçosa, MG. Verificou-se, na seleção entre e dentro de famílias, a eficiência da seleção direta, indireta e com base em índice clássico. Compararam-se as estratégias de seleção entre e dentro, combinada, massal e massal estratificada. Os resultados encontrados pela seleção entre e dentro foram confrontados com os obtidos em seleção realizada, nessa mesma população, no primeiro ano de produção. As características mensuradas foram número de frutos por planta, produção estimada por planta, comprimento do fruto, diâmetro do fruto, massa do fruto, massa da casca, espessura da casca, massa da polpa, coloração da polpa, porcentagem de polpa, teor de sólidos solúveis totais, acidez total titulável e relação entre teor de sólidos solúveis totais/acidez total titulável. Foi obtida amostra de 10 frutos de cada planta, para avaliação das características qualitativas dos frutos. A colheita dos frutos foi feita de forma parcelada durante o segundo ano de produção, de janeiro a julho de 2006. Os frutos destinados à análise foram colhidos a partir do estádio verde-amarelo . Todas as análises estatísticas foram realizadas com o aplicativo computacional em genética e estatística (GENES). Foram estimados os ganhos de seleção em função de uma porcentagem de seleção de 24% entre famílias e 25% dentro de famílias para todas as características mensuradas. O critério de seleção adotado para todas as características foi o acréscimo em suas médias originais, exceto em massa e espessura da casca, em que se buscou o decréscimo. Para escolha das características que fizeram parte do índice clássico de seleção, foi realizado o diagnóstico de multicolinearidade, empregando para isso a análise dos autovalores e autovetores. As características selecionadas para compor o índice foram produção estimada por planta, diâmetro do fruto, porcentagem de polpa, coloração da polpa e acidez total titulável. A utilização da estratégia de seleção simultânea de caracteres, com base no índice clássico apresentou estimativas de ganhos superiores às das outras metodologias em produção estimada por planta e porcentagem de polpa. Na seleção direta, as estimativas de ganhos foram superiores em coloração de polpa e acidez total titulável. A seleção combinada, quando comparada à seleção entre e dentro, massal e massal estratificada, proporcionou as maiores estimativas de ganhos em 11 das 13 características avaliadas, exceto comprimento e massa do fruto, sendo, assim, a estratégia mais apropriada para o melhoramento genético da população estudada. A realização das avaliações no primeiro ano de produção gera resultados satisfatórios, os quais praticamente, se reproduzem no segundo ano, podendo ser recomendada, por reduzir o custo e o tempo de realização do ciclo de seleção.

Made available in DSpace on 2015-03-26T13:55:32Z (GMT). No. of bitstreams: 1 texto completo.pdf: 484099 bytes, checksum: 2183b6947a541e4acdedb364504ccd85 (MD5) Previous issue date: 2007-08-10 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The superior phenotypes selection, in individual or families, is a practice of considerable importance for the improvers , once to obtain improved populations it is necessary to select and matings among or inside of families. This work s aim was to compare the efficiency of some arrangements between the individual selection and the selection among families to get combined selection indexes and soon afterwards to verify a cluster analysis was capable to detect different groups. Through the program GENESYS, it was simulated four genomes, each one considering only one characteristic, varying to each other just in value of heritability; then, we have two characteristics of low heritability (0,20 and 0,10), one of medium heritability (0,40) and one with high heritability (0,60). Using those genomes, bases populations of 1000 individuals (500 males and 500 females) with a rate endogamic equivalent to zero were simulated. In each base population, it was aleatory selected 10 males and 100 females corresponding, respectively, to 2% and 20% of selection intensity. When these individuals selected couple, it was maintained a control of 10 females for each male and, as a result, it was kept an initial population with 1000 descending, also maintaining a balance of 10 descending for female. For each characteristic selections, different arrangements were done to obtain combined selection s indexes. Thus, the first obtained index considers 100% for individual phenotype (Individual); the second considers 90% for individual phenotype and 10% for average phenotypic of the family (09P+01F); the third considers 70% for individual phenotype and 30% for average phenotypic of the family (07P+03F); the fourth considers 50% for the two values (05P+05F); the fifth considers 30% for individual phenotype and 70% for average phenotypic of the family (03P+07F); the sixth considers 10% for individual phenotype and 90% for average phenotypic of the family (01P+09F) and the seventh index considers 100% for the average phenotypic of the family (Family). The selected individuals' matings were driven at random. A final population of 1000 individuals was totaled. Each selection s strategy was led by 20 consecutive generations with 10 repetitions seeking to minimize the mistakes and effects of the genetic flotation. For a larger clarity in the interpretation of the results, a grouping analysis was accomplished by optimization by the method of Tocher in three intervals of time, with the first five generations, with the first ten generations and with the 20 total generations. The behavior of the selection s strategies for different herdability s values was not the same. As smaller the value of the heritability is, the difference among the averages phenotypics in each generation is bigger and the total earnings in these averages are smaller. The combination of the individual value with the family s average was more efficient for the lowest heritabilities. For these heritabilities, the individual selection or among families did not show to be a good option. The selection just through the individual s phenotypic value can be a good alternative for the characteristic of average herdabilidade and it was the best to the characteristic of high heritabilities. / A seleção de fenótipos superiores, sejam individuais ou famílias, é uma prática de considerável importância para o melhorista , uma vez que a obtenção de populações melhoradas passa pela seleção e acasalamentos entre ou dentro de famílias. O objetivo deste trabalho foi comparar a eficiência de alguns arranjos entre a seleção individual e a seleção entre famílias na obtenção de índices de seleção combinada e em seguida verificar se uma análise de agrupamento foi capaz de detectar grupos distintos. Por meio do programa GENESYS foram simulados quatro genomas, cada um considerando uma única característica, variando entre si apenas no valor da herdabilidade; assim, tem-se duas características de herdabilidade baixa (0,20 e 0,10), uma de herdabilidade média (0,40) e uma com alta herdabilidade (0,60). A partir desses genomas foram simuladas populações bases de 1000 indivíduos (500 machos e 500 fêmeas) com uma taxa endogâmica igual a zero. Em cada população base foram selecionados aleatoriamente 10 machos e 100 fêmeas correspondendo, respectivamente, a uma intensidade de seleção de 2% e 20%. Por meio do acasalamento desses indivíduos selecionados, mantendo o equilíbrio de 10 fêmeas para cada macho, obteve-se uma população inicial com 1000 descendentes, também mantendo um equilíbrio de 10 descendentes por fêmea. Para cada característica foram realizadas seleções com diferentes arranjos para obtenção de índices de seleção combinada. Assim, tem-se o primeiro índice que pondera 100% para o fenótipo individual (Individual); o segundo que considera 90% para fenótipo individual e 10% para média fenotípica da família (09P+01F); o terceiro com 70% para fenótipo individual e 30% para média fenotípica da família (07P+03F); o quarto com 50% para os dois valores (05P+05F); o quinto com 30% para fenótipo individual e 70% para média fenotípica da família (03P+07F); o sexto com 10% para fenótipo individual e 90% para média fenotípica da família (01P+09F) e o sétimo índice que considera 100% para a média fenotípica da família (Família). Os acasalamentos dos indivíduos selecionados foram conduzidos ao acaso. Totalizou-se uma população final de 1000 indivíduos. Cada estratégia de seleção foi conduzida por 20 gerações consecutivas com 10 repetições visando minimizar os erros e efeitos da flutuação genética. Para maior clareza na interpretação dos dados foi realizada análise de agrupamento por otimização pelo método de Tocher em três intervalos de tempo, com as cinco primeiras gerações, com as dez primeiras gerações e com as 20 gerações totais. O comportamento das estratégias de seleção para os diferentes valores de herdabilidade não foram iguais. Quanto menor foi o valor da herdabilidade, maior foi a diferença entre as médias fenotípicas em cada geração e menor foi o ganho total nestas médias. A combinação do valor individual com a média de família foi mais eficiente para as herdabilidades baixas. Para estas herdabilidades, a seleção individual e a entre famílias não se mostraram boa opção. A seleção apenas pelo valor fenotípico individual pode ser boa alternativa para a característica de média herdabilidade e foi a melhor opção para a característica de alta herdabilidade.

Les SIEMs (systèmes pour la Sécurité de l'Information et la Gestion des Evénements) sont le cœur des centres opérationnels de sécurité actuels. Les SIEMs corrèlent les événements en provenance de différents capteurs (anti-virus, pare-feux, systèmes de détection d'intrusion, etc), et offrent des vues synthétiques pour la gestion des menaces ainsi que des rapports de sécurité. La recherche dans les technologies SIEM a toujours mis l'accent sur la fourniture d'une interprétation complète des menaces, en particulier pour évaluer leur importance et hiérarchiser les réponses. Toutefois, dans de nombreux cas, la réponse des menaces a encore besoin de l'homme pour mener l'analyse et aboutir à la prise de décisions, p.ex. compréhension des menaces, définition des contremesures appropriées ainsi que leur déploiement. Il s'agit d'un processus lent et coûteux, nécessitant un haut niveau d'expertise, qui reste néanmoins sujet à erreurs. Ainsi, des recherches récentes sur les SIEMs ont mis l'accent sur l'importance et la capacité d'automatiser le processus de sélection et le déploiement des contremesures. Certains auteurs ont proposé des mécanismes automatiques de réponse, comme l'adaptation des politiques de sécurité pour dépasser les limites de réponses statiques ou manuelles. Bien que ces approches améliorent le processus de réaction (en le rendant plus rapide et/ou plus efficace), ils restent limités car ces solutions n'analysent pas l'impact des contremesures choisies pour atténuer les attaques. Dans cette thèse, nous proposons une nouvelle approche systématique qui sélectionne la contremesure optimale au travers d'un ensemble de candidats, classés sur la base d'une comparaison entre leur efficacité à arrêter l'attaque et leur capacité à préserver, simultanément, le meilleur service aux utilisateurs légitimes. Nous proposons également un modèle pour représenter graphiquement les attaques et les contre-mesures, afin de déterminer le volume de chaque élément dans un scénario de multiples attaques. Les coordonnées de chaque élément sont dérivés d'un URI . Ce dernier est composé principalement de trois axes : l’utilisateur, le canal et le ressource. Nous utilisons la méthodologie CARVER pour donner un poids approprié à chaque élément composant les axes de notre système de coordonnées. Cette approche nous permet de connecter les volumes avec les risques (p.ex. des grands volumes sont équivalents à des risques élevés, tandis que des petits volumes sont équivalents à des risques faibles). Deux concepts sont considérés en comparant deux ou plusieurs volumes de risques: le risque résiduel, qui résulte lorsque le volume du risque est plus élevé que le volume de la contre-mesure, et le dommage collatéral, qui en résulte lorsque le volume de la contre-mesure est supérieur au volume du risque. En conséquence, nous sommes en mesure d'évaluer les contre-mesures pour des scénarios d'attaques individuelles et multiples, ce qui permet de sélectionner la contre-mesure ou groupe de contre-mesures qui fournit le plus grand bénéfice à l'organisation / Current Security Information and Event Management systems (SIEMs) constitute the central platform of modern security operating centers. They gather events from various sensors (intrusion detection systems, anti-virus, firewalls, etc.), correlate these events, and deliver synthetic views for threat handling and security reporting. Research in SIEM technologies has traditionally focused on providing a comprehensive interpretation of threats, in particular to evaluate their importance and prioritize responses accordingly. However, in many cases, threat responses still require humans to carry out the analysis and decision tasks e.g., understanding the threats, defining the appropriate countermeasures and deploying them. This is a slow and costly process, requiring a high level of expertise, and remaining error-prone nonetheless. Thus, recent research in SIEM technology has focused on the ability to automate the process of selecting and deploying countermeasures. Several authors have proposed automatic response mechanisms, such as the adaptation of security policies, to overcome the limitations of static or manual response. Although these approaches improve the reaction process (making it faster and/or more efficient), they remain limited since these solutions do not analyze the impact of the countermeasures selected to mitigate the attacks. In this thesis, we propose a novel and systematic process to select the optimal countermeasure from a pool of candidates, by ranking them based on a trade-off between their efficiency in stopping the attack and their ability to preserve, at the same time, the best service to normal users. In addition, we propose a model to represent graphically attacks and countermeasures, so as to determine the volume of each element in a scenario of multiple attacks. The coordinates of each element are derived from a URI. This latter is mainly composed of three axes: user, channel, and resource. We use the CARVER methodology to give an appropriate weight to each element composing the axes in our coordinate system. This approach allows us to connect the volumes with the risks (i.e. big volumes are equivalent to high risk, whereas small volumes are equivalent to low risk). Two concepts are considered while comparing two or more risk volumes: Residual risk, which results when the risk volume is higher than the countermeasure volume; and Collateral damage, which results when the countermeasure volume is higher than the risk volume. As a result, we are able to evaluate countermeasures for single and multiple attack scenarios, making it possible to select the countermeasure or group of countermeasures that provides the highest benefit to the organization