— Information and Communications Technologies (ICT) are fostering the appearance of a plethora of new services and applications. On the one hand, ICT will improve the efficiency of a variety of processes (e.g. supply chains, e-commerce, etc.) and they will make easy the development of new services. On the other hand, the massive deployment of these new technologies may lead to the invasion of users privacy. In this article, we analise four of the main technologies which can put the privacy of their users in jeopardy: Internet browsing, location-based services, RFID technology and statistical databases.