The Nature and the Evolving Trends of the Cyber Threat and of the Vulnerabilities of the National ICT Infrastructures Cyber vulnerabilities to ensure continuity of the service and to minimize the impact of natural events on physical infrastructure. Technical vulnerabilities are instead due to the vulnerabilities of hardware and software, and to faults in communication protocols. The latter are particularly worrisome when they affect the Domain Name System (DNS), because they impact both ends of the systems, that is to say the final electronic communication users as well as the supervisory control and data acquisition systems of critical infrastructures connected to the Internet. Cyber attacks undermine users’ trust in ICT technologies and impair business continuity by exploiting organizational, procedural and technical vulnerabilities – often in various combinations. Organizational and procedural vulnerabilities depend both on the deficient implementation of protection against malware – such as inappropriate network design, update of anti-viruses and anti-spam software – and on the lack of appropriate physical protection intended 17