In an era that has seen a multitude of high impact disasters ranging from natural events such as earthquakes, floods, tsunami’s, volcanic disruptions to man-made acts of terrorism and cyber attacks, there is a greater need than ever before to ensure that modern societies are well equipped and prepared to withstand and recover from such unexpected adverse events. To guarantee societal preparedness and recovery, attention has been channelled to reducing the vulnerability of the important CI systems which support the economic, environmental and security activities of modern societies.
Against this backdrop, tailored made operable concepts of resilience offering all encompassing, integrated approaches to planning for, responding to and recovering from all manner of man-made and natural disasters that can be implemented by the CI have been increasingly sought.
Resilience is now a central concept in crisis and disaster management discourse, and is the focus of widespread efforts for resisting, absorbing, accommodating and recovering from the effects of man-made and natural threats.
The effects of CI failures as illustrated by events such as the Tohuku earthquake in Eastern Japan or Hurricane Sandy in New York show how a breakdown in CI systems can bring about catastrophic consequences. Furthermore, with increased dependencies between different CI systems i.e. water supply dependent on electricity for pumping stations, modern banking depending on ICT and fire services dependent on water supply, the cascading effects of a breakdown in one system on other interconnected systems, is also of significant concern. A fault in an electricity transmission network in Northern Germany which resulted in a blackout for more than 15 million people across Western Europe in 2006 exemplifies the type of cascading effects on transport, healthcare systems, financial services and societal security and safety that can quickly arise when there is a failure of critical infrastructure. Another example of the importance of resilience efforts to safeguarding CI arose when a Russian-Ukraine gas dispute escalated in 2009 resulting in a major disruption to the gas supply of many European States with thousands of homes and business left without electricity. As these examples illustrate, CIs are increasingly connected to the functioning of society and economy and is of paramount importance to the quality of life, security and well-being of all European citizens.
Therefore where the interest in resilience has been largely shaped by recent disaster events and their social consequences, so too has the focus on CI resilience sprung from the need to minimise critical service disruptions, accidents and in particular, cascading failures.
A working definition for Critical Infrastructure Resilience (CIR) has been provided for use in the RESILENS project. It defines CIR as:
 Union for the Coordination of the Transmission of Electricity (2006) Final Report System Disturbance on 4 November 2006.
“a transformative, cyclical process, that builds capacities in technical, social and organisational resources for critical system function, so as to mitigate the impacts of disruptive events and long-term incremental changes, thus guaranteeing the continued provision of its basic functions. CIR is based upon new forms of risk management, adaptability and the assessment of potential trade-offs between parts of a system”.