Security is a social practice which involves a wide spectrum of actors. Instead of relying on a simplistic distinction between state and non-state entities, this book analyzes security practices, considering exchange relations between providers and receivers of security. This departs from the still dominant imagery that charts ongoing transformations in the global security landscape along a series of categorical divisions between state and non-state or between the public and the private. The book argues that a more rewarding analytical perspective adopts a system of differentiation based upon the production and exchange of security. Contents include: security: what is it? what does it do? * governing security * security networks * the political economy of security * compulsory security formations * commercial security formations * conceptual variations * strategic variations * structural variations. Dissertation.