Active assisted living (AAL) environments inherently collect, generate, and use large amounts of data. These environments are inherently distributed and often use external services, so data can be in different states and locations. This data is often very sensitive, and its compromise can endanger the privacy and security of users. Additionally, data unavailability can jeopardize the proper functioning of critical environment functions. This chapter presents relevant aspects of data protection. General principles, risks, approaches, and solutions for data protection are analyzed, taking into account the specificities applicable in AAL environments. The first part of the chapter provides an overview of security and data protection, along with a chapter outline. The second part offers a retrospective of the evolution of relevant information technologies, with an emphasis on two critical technologies for AAL: the Internet of Things and cloud computing. The third part outlines the relevant cryptological fundamentals of data protection. In the fourth part, a synthesis of the fundamentals, technologies, risks, and possible solutions is presented. The fifth part of the chapter expands the view on data protection from the perspective of the importance of open source and technological sovereignty. The sixth part reviews the importance of proper management of the entire lifecycle of AAL environments and their components. Finally, the last part of the chapter analyzes relevant and current legal aspects of data protection.