Computer network monitoring application is one of the most useful technologies nowadays. It provides an easy way to monitor computers from a distance. SNMP has packages that contain network information. The network information includes specification which can be used to identify whether nodes in the network is connected or not. The main purpose of the research is to create a computer network monitoring application that can determine which computer is connected to network. The application is not only identifying the connection but also time of connection or disconnection. When a computer is connected or disconnected, there is a message as an indicator. The application also can detect if an intruder connect to the network. Intruder can not communicate with another computer in different subnet. The computer network monitoring application has accomplished the intended results. The application can retrieve information from network about the status of computers and the details. The details of status are about time of connection and disconnection. The average percentage of success for periodic information (memory and cpu usage) is 85%. The application also detect intruder successfully and block it connection to another subnet including internet connection.