CCTVs have invaded our cities and spy all our actions. Increasingly, these mass surveillance devices represent a critical issue as far as our need for privacy is concerned. Furthermore, the data collected by CCTVs are processed more and more by private operators and companies. One of the main threats is that these data are then exploited for illegitimate uses or for commercial interests. In a context of urban guerilla (e.g. street riots against dictatorship), CCTVs can be exploited by non-democratic countries to track political opponents. For reasons of cost, most of these cameras are rather basic devices and their security can be easily circumvented.