The increasing complexity of information and telecommunications systems and networks is reaching a level beyond human ability, mainly from the security assessment viewpoint. Methodologies currently proposed for managing and assuring security requirements fall short of industrial and societal expectations. The statistics about vulnerabilities and attacks show that the security, reliability and availability objectives are not reached and that the general threat situation is getting worse. With the deployment of Next Generation Networks – NGNs, the complexity of networks, considering their architecture, speed and amount of connections, will increase exponentially. There are several proposals for the network and security architectures of NGNs, ...