Massive numbers of applications have been developed to fulfill the requirements of end-users; the world is considered as a cell of communication in which applications are centralized and distributed, and accessed by internet. Like traditional networks, real time networks such as supervisory control and data acquisition (SCADA) systems, distributed controller systems (DCSs) and others have been employing the internet technology to connect their various stations, and with central controller(s). Internet technology brought several benefits in terms of real time delivery of information to, and between geographical located stations; but at the other side, numerous of security issues have also been accounted and considered to be dangerous for information delivery. In survey, numbers of vulnerabilities and security issues are identified by reviewing of existing researches in real time networks, existing security developments are also reviewed and analyzed, and future directions are highlighted that will enhance the security in real time transmission(s).