This edited volume explores the fundamental aspects of the dark web, ranging from the technologies that power it, the cryptocurrencies that drive its markets, the criminalities it facilitates to the methods that investigators can employ to master it as a strand of open source intelligence. The book provides readers with detailed theoretical, technical and practical knowledge including the application of legal frameworks. With this it offers crucial insights for practitioners as well as academics into the multidisciplinary nature of dark web investigations for the identification and interception of illegal content and activities addressing both theoretical and practical issues.