Security practices at the EU level are increasingly fuelled by technologies of control and surveillance of individuals, as well as by exchanges of know-how and mass-data between and within EU members. This complex process involves a wide array of interconnected and interacting institutions and agencies at the national, European and international levels (Bigo et al. 2007b). In this context, one of the initial objectives of the CHALLENGE project was to draw a precise map of the positions of security agencies in Europe in order to see how the professional solidarities and struggles restructure power relations at the national, EU and transatlantic levels. The notion of ‘field of security professionals’ was used to describe the space of competition between agencies and institutions over the pertinent knowledge concerning threats, risks and vulnerabilities.