Even more than today, information and communication technologies (ICT) will form the information and control backbone of all critical infrastructures. This generates new opportunities for their effective and efficient management. But at the same time it generates new vulnerabilities. A loss of ICT functionality will severely influence the operation of critical infrastructures. Until recently, large critical infrastructures operated on their own, independent information and control infrastructures. In the future this will be possible only in rare exceptions (for instance, for the European transnational power grid). Most critical infrastructures will rely on external telecommunication networks not under their own control. This generates new dependencies which need adequate treatment.