Measures to Ensure the Sustainability of Information Systems in the COVID-19 Environment

National defense requires uninterrupted decision-making, even under direct or indirect impacts of non-traditional threats such as infectious diseases. Since all work utilizes information systems, it is very important to ensure the sustainability and availability of information systems. In particular, in terms of security management, defense work is being performed by dividing the network into a national defense network and a commercial Internet network. This study suggests a work execution plan for sustainability that takes into account the efficiency of work performed on the Internet and the effectiveness of security through effective defense information system operation. It is necessary to minimize the network contact points between the national defense network and the commercial Internet and to select high-priority tasks from various tasks and operate them efficiently. For this purpose, actual cases were investigated for an institution, “Organization A”, and characteristics were presented. Through the targeted tasks and operation plans presented in this paper to improve the effectiveness of defense tasks and ensure security, it will be possible to increase the sustainability and availability of task performance even under non-traditional threats such as infectious diseases.