Welcome to this special issue of the Journal of Computer Virology and Hacking Techniques on Knowledge-based System and Security. The main goal for this special issue is to be a timely vehicle for publishing selected research papers from academia and practitioners in different industries on this emerging topic. Knowledge-based security systems are developed to ensure computer virology-making by effectively using timely and appropriate knowledge base, security management, hacking techniques for convergence [11][12][13][14]. This special issue covers some of the hottest topics in knowledge-based system and security, including: Privacy and authentication for wireless network; Convergence security in ubiquitous computing; Algorithmic and computer virology; Innovative applications of ubiquitous computing; Intelligent applications for security processing; Hacking, Knowledge processing algorithms; User experience in knowledge security systems, embedded systems security; Personalization, privacy, computer virology, Information indexing; computer virology; Cryptology and embedded systems; Security applications in computer virology.The paper by Lee [1] presents a secure game development method for the Internet of Things (IoT). The proposed method for developing a game in the IoT service environment looks at the length-related password vulnerability and introduces a method with which a hacker lures Internet users and seizes the users' IDs and passwords, as well as their password generation patterns. An additional improved process is