Power system (PS) is exposed to natural and man-related threats which may affect the security of power supply, depending on the vulnerabilities of the system to the threats themselves as well as on the pre-fault operating conditions. Threats regard not only the power components, but also the Information and Communications Technology (ICT) systems involved in PS control and protection. The resulting picture is characterized by significant uncertainties, especially as far as high impact, low probability (HILP) events (typical causes of blackout events) are concerned. These considerations call for the adoption of novel techniques to perform more in-depth security analyses, able to identify the contributions of the different threats and vulnerabilities to the overall operational risk. The paper describes a probabilistic risk-based methodology, developed within the European Union (EU) research project called AFTER (A Framework for electrical power sysTems vulnerability identification, dEfense and Restoration), aiming to perform risk assessment (by means of hazard, vulnerability, and impact analysis) of the integrated power and ICT systems. Preliminary examples are proposed on a test system.