Security intelligence continues to be of central importance to the contemporary world: individuals, groups, organizations and states all seek timely and actionable information in order to increase their sense of security. But what exactly is intelligence? Who seeks to develop it and to what ends? How can we ensure that intelligence is not abused? In this third edition of their classic guide to the field, Peter Gill and Mark Phythian set out a comprehensive framework for the study of intelligence, discussing how states organise the production - collection, analysis and dissemination - of intelligence, how it is acted upon, why it may fail and how the process should be governed in order to uphold democratic rights. Fully revised and updated throughout, the book covers recent developments including the impact of the Snowden leaks on what is known about the role of intelligence agencies in the surveillance of the Internet and social media, their involvement in cyber operations and the legal and political arrangements for democratic control. The role of intelligence as part of 'hybrid' warfare in the case of Russia and Ukraine is also explored and the problems facing intelligence in the realm of counter terrorism considered in the context of the current wave of attacks in Western Europe. Intelligence in an Insecure World is an authoritative and accessible guide to a rapidly expanding area of inquiry - one which everyone has an interest in understanding.