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Because of distributed nature, grid computing environments are easy targets for intruders looking for possible vulnerabilities to exploit [1]. By impersonating legitimate users, the intruders can use a service's abundant resources maliciously. To combat attackers, intrusiondetection systems (IDSs) can offer additional security measures for these environments by investigating configurations, logs, network traffic, and user actions to identify typical attack behavior. However, IDS must be distributed to work in a grid computing environment. It must monitor each node and, when an attack occurs, alert other nodes in the environment. This kind of communication requires compatibility between heterogeneous hosts, various communication mechanisms, and permission control over system maintenance and updates. We present the problem of grid intrusion; analyze the requirements of a system to detect them. In this paper we are discussing how IDS can be implemented for grid computing environment.

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City 600 026 -Jawaharli Nehru Salai (100 feet Road) -Vadapalani Chennai -Tamil Nadu -India 3 Universidade de Federal -UFAL/ICAT Campus A. C. Simões, BR 104 Norte Km 97 -57072-970 -Maceió -AL, Brasil Artigo recebido em 15/08/2011 e aceite em 15/09/2011 A B S T R A C TThe results indicated that the effect caused by the El Niño event in the various types of vegetation in the semi-arid region of Northeast Brazil during the last two decades of the last century, presented a differing seasonal and interannual patterns from the vegetation types in the African Sahel. The seasonal amplitude of Normalized Difference Vegetation Index -NDVI variation in the African Sahel was not altered by the climatic effect of El Niño, however, in the semi-arid region of Northeast Brazil, the vegetation types were affected during the El Niño events. Furthermore, it was observed that the NDVI varies according to the local climatic conditions, presenting a temporal gap between the precipitation occurrence and water absorption available from the vegetation. This information is important to show contour conditions for climatic models and also for the weather numerical forecasting. Análise da Dinâmica Temporal do NDVI nos Ecossistemas Semi-áridos: CaatingaBrasileira e Sahel Ocidental Africano R E S U M O Os resultados indicaram que o efeito causado pelo evento El Niño, nos vários tipos de vegetação na região semi-árida do Nordeste do Brasil, durante as duas últimas décadas do século passado, apresentou diferentes padrões sazonais e interanuais dos tipos de vegetação no Sahel africano. A amplitude sazonal na variação do Índice de Vegetação Diferença Normalizada -NDVI, no Sahel Africano não foi alterada pelo efeito climático do El Niño, no entanto, na região semi-árida do Nordeste do Brasil, os tipos de vegetação foram afetados durante os eventos El Niño. Além disso, observou-se que o NDVI varia de acordo com as condições climáticas locais, apresentando uma lacuna temporal entre a ocorrência de precipitação e absorção de água disponível na vegetação. Esta informação é importante para mostrar condições de contorno para os modelos climáticos e também para a previsão numérica de tempo. Palavras-chave: Vegetação, Aridez . Satelite

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