This simple book teaches you how to write a Ransomware. Hopefully the source code we have written in the book will get you started in the right direction. Ransomware is a type of worm that often limits a user from accessing his or her computer system, either by locking the computer system's screen or by encrypting or locking files unless some ransom is paid. Most often ransomware worms are categorized as crypto-ransomware, because they encrypt certain file types on the infected systems and forces the owner of the system to pay some ransom through an online payment portal to get the decrypt key.