This book would help the digital security people ongoing through the contents in this scenario. Mainly the book includes the definition of the most effective threats/attacks, such as APTs, particularly its anatomy, of the steps involved in APTs. Nowadays, most of the data that would store, process, analyze, and communicate through cloud-only. The book describes data security in the cloud storage system in this respect, by following CIA Triad. Additionally, the book describes APT's defense mechanism in networks and clouds. In addition, the book describes verifiable encryption and decryption by following the OFE (Optimistic Fair Exchange) prover and verifier mechanism. It narrated an intrusion detection system model for the design of low false-rate alarms using Machine Learning Techniques. Observation and analysis have been given in the book; this would be helpful for teachers, scholars, and faculty who are involved in this area of study.