Security has always been a major concern of network operators. Despite a pretty rich security toolbox that never ceased to improve over the years (filters, traffic wells, encryption techniques, and intrusion detection systems to name a few), attacks keep on increasing from both a numerical and amplitude standpoints. Such protean attacks demand an adapted security toolkit that should include techniques capable of not only detecting these attacks but also anticipating them even before they reach their target. Strengthening future networking infrastructures so that they become protective, instead of being “just” protected must thus become one of the key strategic objectives of network operators and service providers who ambition to rely upon robust, dynamic, security policy enforcement schemes to develop their business while retaining their existing customers. This chapter discusses the various security challenges that may be further exacerbated by future networking infrastructures. It also presents some of the techniques that are very likely to become cornerstones of protective networking.