Different processes in the last twenty-five years have transformed the understanding of borders and international mobility, with an increasing number of people on the move and borders that multiply beyond the territorial limits of the state. Alongside these processes that alter the speed of movement, create new pathways for circulation and offer new forms of surveillance and blocking of individuals, the interpretation of borders is being redefined seeking to account for these new processes, both to facilitate them and to prohibit them. Following these changes in the understanding of borders and with a history of constant innovations in immigration policies, Australia in 2013 adopted the Operation Sovereign Borders, an operation that encompasses several of these transformations in seeking greater control and by using more violence against asylum seekers. The Operation Sovereign Borders created and institutionalized new immigration control practices, being permeated by a specific rationality of the fear of invasion and supported by extensive and controversial legislative innovations. This dissertation presents the transformations of borders and their interpretations, exploring the Australian case, its field of migration and border control, the actors in this field, its legislative structure, its rationality and practices.