This proceedings volume presents a collection of articles from key practitioners from relevant areas with experience in critical infrastructure. The authors acknowledge that the responsibility for critical infrastructure protection is primarily a matter of international importance, hence a high degree of cross-border and cross-sectoral interdependencies must be coordinated or, where appropriate, legally harmonized efforts at the international level, including the smooth functioning of the internal policies. The book focuses on countering hybrid threats that render critical infrastructures vulnerable. An understanding of such threats will render critical infrastructure safe, secure, and resilient. The protection of national critical infrastructures, as well as of the functions and services critical to the proper functioning of society is a key priority and requires a new unique and strategic approach. Work in this direction must consider the strong interdependencies between the various critical functions and services, including financial services, the key role of the private sector, the changing security environment, and emerging risks, both in the physical and cyber fields. In addition to legal requirements, agreements should be promoted with private sector infrastructure and service owners and operators to ensure the continuity of and access to critical services, including beyond force majeure, by ensuring an acceptable level of preparedness to respond. all relevant threats, as well as the flexibility to address and mitigate the effects of low-probability, high-impact events.