Security is one of the main concerns in current telecommunication net- works: the service providers and individual users have to protect themselves against attacks, and to this end a careful analysis of their optimal strategies is of essential importance. Indeed, attackers and defenders are typically agents trying strategically to design the most important damages and the most secure use of the resources, re- spectively, and the natural modelling framework of these interactions is that of non- cooperative game theory. This chapter aims at providing a comprehensive review of game-theoretic aspects of security. We first describe the basics on game theory through simple security problems, and then present and discuss some specific prob- lems in more detail. Finally, we also deal with security economics, focusing on the selfish relationships between customers and providers as well as between competing providers, which represents another important aspect of our non-standard approach towards security risk assessement.