The book "Biometric User Authentication for IT Security" offers a comprehensive introduction to the techniques of biometric user authorization, which are of great interest in both academia and industry. It covers the fundamental principles of passive biometric recognition, which includes physiological traits such as fingerprints, iris, and facial recognition, as well as active recognition, which considers learned behaviors like voice, handwriting, and gait. Notably, it provides a detailed analysis of handwriting as an active biometric technique, which is often overlooked in other publications. The book addresses various aspects, including the dependence on sensor characteristics, potential attack scenarios, and the generation of cryptographic keys from handwriting. It is aimed at professionals and enthusiasts who wish to gain a deeper understanding of the challenges and opportunities of biometric authentication in the field of IT security.