The SmartPSS application features a Log module that you can access to see who and when connected to the cameras. If the log doesn't display anything, then you can connect to each camera individually and access its access logs.
I have a MileSight CMS and it has the same interface as the SmartPSS. The Log provides who is connected and when did he/she connect to the streaming interface.
However, try changing the default passwords to the cameras to remove access for others to connect.