Abstract: In order to overcome the provisioning and scalability limits of a single cloud, cloud federation appears as the computing model in which multiple resources from independent cloud providers can be shared to create large-scale distributed virtual clusters. On the other hand, these complex architectures become an attractive target for distributed denial of service (DDoS) attacks. Although, federated cloud environments have large amount of resources and profound dynamic allocation capability, which can be used to face DDoS attacks, they are however vulnerable to attacks that aim at compromising the service level agreements. In this paper, we investigate the key research topics for supporting distributed intrusion detection in a federa...