Analyze the packets, to find the source port number. Use this port number in a tool like cports, to obtain process id. You can track the process name and its respective executable from the pid in task manager. Check if that process is one, which you have initiated, or is it doing any thing useful to your work. If not then kill that process. Moreover, if that process is activated everytime, when you starts your machine, then may be it'll be a startup program/service or a scheduled task, which you have to disable and remove.