Mobility and the new global economy are accompanied by requirements for dynamism and flexibility, with respect to e-commerce, inter-organizational activity, and security. The classical approach to computer security, typified by firewalls, is no longer suitable to encourage and facilitate the growth and nomadic collaboration foreseen for current and future corporate environs. This paper investigates the nature of firewalls, their concepts, goals, history and implementations, in order to determine the validity of the claims of inadequacy made. We present arguments surrounding these claims from both business and technical perspectives. This includes consideration of real-world scenarios and identification of the fundamental concerns for corporate network administration. We further present possibilities for application level security to address the shortfalls of firewalls and providing end-to-end security over heterogeneous networks. This includes a formal definition, proposed architecture, comparison to firewalls, and references to existing technologies and research in this direction.