In contrast to the offline world, any activity in the online world leaves digital traces which can be stored, collected, combined and analyzed. This data can not only be accumulated to provide information on communication patterns or on the online user´s whereabouts, it also can disclose personal interests, political attitudes, or sexual predispositions. Once digitally captured, these data remain accessible and may be analysed. Various uses and abuses can be made of the data: at the same time the lines dividing these categories are blurred. The principles of explicit consent and usage limitation are not easy to follow in view of the increasingly invisible and hence unnoticed collection of data, their transfer and use in different contexts, and the time spans between collection and exploitation. From the point of view of data protection the prevention of collection therefore plays a central role in privacy policies. However, individual possibilities are often limited.
The study "Data prevention in practice" discussed and analysed the limits of individual responsibility. The study identified those areas in which consumer organisations, policy makers and industry are required to reach voluntary or compulsory agreements for the protection of privacy. The areas of private Internet use, data mining and smart cards for citizens were analysed in detail. Concrete recommendations were developed for these aereas and the need for policy intervention was identified.