On the effective exploitation of distributed information for cooperative network security and routing optimization.

The wide deployment of more and more sophisticated services and application over Internet imposes to careful project solutions for face the threats that this spreading involved. Unfortunately, the computer networks were de- signed neglecting the problem of security, since they ware thinking as "open systems" where anyone could use them as it liked, and malicious users was not considered. The lack of security requires to study alternative solutions that integrate the existing network technologies. The interest in computer network security is growing in the last year and new ideas have been proposed. In this thesis we present a cooperative approach to network security. By sharing information about evidence of anomalous user's activities it is possible to improve the effectiveness of the overall system by a careful prevention and detection of attacks. In this way the cooperation is able to overcome the intrinsic design limits of existing computer networks. By analyzing several collaborative systems, we de ne a general framework for the design and implementation of a reliable cooperative solution. Based on this framework, we implement two systems that share common project's principles: a cooperative DoS detection system and a new secure routing protocol for wireless networks. The results prove the goodness of design and the capability of framework proposed to be extended to several problems of network security.