Wireless sensor network (WSN), Mobile ad hoc networks (MANET) and Internet of Things (IoT) are emerging and successful technologies which are being used in various application domains in real life. Implementing security solutions in such advanced networks is one of the considerable challenge due to limited resources such as energy, mobility, scalability, and computational ability among others. If any application is aware of its specific security sensitivities that means if the application is executed with sensitive information or data, for example, a smart healthcare system enabled with sensors, IoT and cloud server handles patients’ health and disease-related data which is of privacy and security sensitive. In such systems the communicating nodes are geographically distributed and communicate with each other through security attack and threat prone open wireless links enabled with Wi-Fi, 3G/4G internet connection etc. In such applications security attacks, threats, vulnerabilities need to be identified properly for implanting preventive measures or providing security solutions once attacks are detected. This chapter traverses through different security attacks, threats, proposed solutions and a summary of funded research projects by different international reputed funding agencies along with budget information to reflect the importance and significance of security aware solutions in WSN, MANAET, and IoT.