This thesis deals with the theme of protection of the privacy on the Internet and the role of libraries in it as well as fight against mass surveillance. The work is divided into two parts, the theoritical part which is based on the literature, and the research part. The theoretical part contains the concepts and definitions of privacy and protecting the privacy on the Internet, along with the role of libraries in that protection and the concept of mass surveillance by the governments and intelligence agencies, such as the US National Security Agency (NSA) and its programs for surveilling of millions of people around the world. Also, the theoretical part deals with the library fight against mass surveillance and services that librarians use and educations carried out in order to protect users' privacy on the Internet. The research part of the work deals with the investigation conducted by the survey among students of Information Sciences at the University of Zadar, whose goal was to find out how students protect privacy on the Internet and find out their opinions on the role of libraries in the protection of privacy on the Internet and the fight against mass surveillance. The research wants to alert future librarians about the dangers of violation of privacy on the Internet and mass surveillance that threatens their privacy and privacy of library users. This work is intended as a basis for further research on the topic and the possible implementation of education in libraries as well as pointing out the problems that threaten privacy on the Internet.