Blocking atypical IP address

CIS is giving me a warning about a specific IP address accessing my computer and having access to viewing what I am doing. I have tried to get the IP address blocked but it is an atypical IP Address and there seems to be no way to block it other than going to the task manager to view incoming and out going activity and blocking it each and every last single time. For example: - three digits dot three digits dot one digit dot then the atypical two digits SLASH two digits. I have tried blocking an IP address range, and apparently that does not work.