Although network security theory forbids many connections to large networks as being too risky, the reality is that large numbers of sensitive systems are connected to the Internet and that connectivity is increasing at a rapid rate. Firewalls and host protection mechanisms are used in a somewhat arbitrary fashion, depending more on the availability of products than on a clear understanding of security principles. We need to expand security theory to protect large networks. This paper proposes a new paradigm for security in large networks, based on an understanding of the sometimes conflicting requirements for security, connectivity and functionality. The paradigm, called FICS-IT (Functional, Information, and Connection Security for Information Technology), consists of a philosophy, an approach, a framework and a collection of components. It is based on an understanding of security as risk management and includes: local resource control; multiple, tailored security policies; layered, functional access control; and recognition of heterogeneity in architecture, ownership and policy.