A review of internet censorship: Modern measurement and circumvention techniques

As Internet censorship continues to be deployed across a number of nation-states, understanding its scope and underlying mechanisms is more important than ever. Consequently, research on censorship measurement and circumvention has attracted growing academic interest, particularly in recent years. This article provides an overview of the current state of the art in the field of Internet censorship measurement and circumvention research. First, a brief overview of the fundamentals is provided, followed by an in-depth analysis of 146 contemporary Internet censorship measurement and circumvention studies, predominantly those published within the last ten years, by applying a semi-systematic literature review methodology. Subsequently, the review briefly summarizes the ethical considerations in the field, it visualizes the geographical focus of censorship measurement studies, and it provides an overview of Internet protocols used to measure censorship. In addition, it presents a taxonomy of censorship circumvention tools, analyzes their key characteristics, and examines the prevalence of the underlying network protocols used in circumvention tools. The findings suggest that, while there are numerous solutions for circumventing censorship, many are niche or theoretical, and their practicality remains unknown. Although there is an observable trend toward large-scale longitudinal censorship measurement studies, the realworld effectiveness of (academic) censorship circumvention methods is rarely evaluated. Since both censorship measurement and circumvention research go hand-in-hand, there is an increasing number of measurement studies which directly translate their findings into practical circumvention strategies.