Understanding the nature of systemic risk and identifying the channels of diffusion of the shocks are the necessary prerequisite to anticipate and manage successfully the insurgence of financial crises. In order to prevent financial distress and manage instability, the macroprudential regulator needs to track and measure systemic risks ex-ante. The aim of the paper is twofold: on one side, it reviews the theoretical frameworks which allow to assess the different dimensions of systemic risk and, on the other, it classifies accordingly and analyzes the methodologies available to assess in advance the occurrence of systemic distress. The paper classifies the different definitions of systemic risk and discusses their significance during the 2007-08 crisis. It presents the tools available to extract real time information on market perception of risk from market prices of securities and derivatives (i.e. CDS and equity options). The analysis is extended to the methods focused on the measurement of the financial fragility due to the networks linkages within the financial system. On the basis of the available empirical research, the paper also reviews the capacity of the different methods to spot in advance the insurgence of the crisis prior to 2007-08 and draws some preliminary conclusions on the completeness and consistency of the toolkit available to policy makers
