Specialist work deals with the topic of violation of privacy of the Internet users and the impact of social networks on it. Technological progress and the emergence of the Internet enabled the emergence of social networks, and it was social networks that laid the foundation for the emergence of new services based on the Internet platform that displace traditional electronic communication services. New services offer more than traditional electronic communication services, but in return for being able to use them, they generally require the user's consent to the collection and processing of personal data. The possibilities of new technologies and the collection and processing of personal data have created circumstances in which unhindered communication, secrecy of correspondence, and freedom of expression are threatened, i.e. the right to privacy of the individual guaranteed by legal regulations and international agreements is threatened, and the protection of personal data has become the primary measure by which the right to privacy of Internet users is achieved. The content of the paper is diveded in four parts. First part analyses the number of Internet users and the number of social network users, points out on the increase of new communication services in the world that are replacing traditional ones, such as SMS, and which for the most part are not legally regulated and create the need for interventions in the regulatory framework. Second part defines privacy of Internet users, analyses majority of relevant documents that are intended to protect privacy of Internet users, with concrete examples of privacy abuse, parallel to analysis, points out on the disadvantages of that documents in comparison with the challenges that new technologies and new services bring. Third part analyses the concept of networking, data sharing, user behavior which are partly or entirely implemented through social networks and points out on the new threats on user privacy and the privacy of society as a whole. Furthermore, it analyses the recomendations of work groups and international bodies for increasing security of social network user privacy. Four part analyses number of Internet users and social network users in Republic of Croatia, their habits and knowledge of legal regulations.