A PN can provide the opportunity to personalize applications, services and the whole networking environment to the current needs of the user, making the security and privacy the key features in the PNs formation. In MAGNET Beyond the interest was concentrated on the importance of interactions between multiple PN users with common interests for various services, i.e. on PN Federation (PN-F). Establishing a PN Federation, the user should be able to control which information or services to share with others. For this reason the security is a very important aspect in PN-F as multiple people are involved and takes place at different levels: access to the PN Federation based on membership, secure transport of data within the federation and the access rights to resources and services of the federation. In this chapter, we present important contributions in the study of security of personal networks. To begin with, a threat analysis methodology tailored for PN and PN-F environments is described and applied to evaluate security. A reflection on user perspectives mapped onto security applications, privacy safeguarding and related protocols is encapsulated into the proposed Context Aware Security Manager component. Finally, we present a novel authentication protocol right tailored to specific low power devices needs