In the context of these camera interfaces, the mode parameter usually dictates what the user sees. Common values include:
Secure methods for remote viewing:
that have been left accessible to the public internet without proper password protection. How the "Dork" Works
The viewerframe?mode=motion page is the HTML wrapper that holds the <img> tag refreshing the MJPEG stream. Because this stream is delivered over standard HTTP (not HTTPS) and often has Zero authentication, it is inherently vulnerable.
Regularly check for manufacturer updates to patch security holes.