When a network camera is connected to the internet without a firewall or password, its internal viewing page (the "ViewerFrame") becomes publicly accessible. Search engines like Google crawl these pages, indexing the unique URL structures.
A Google Dork is a specialized search query that uses advanced operators to find information that is not meant to be public but has been indexed by search engines. In this case, inurl: instructs Google to look for specific text within a website's URL. How the viewerframe Exploit Works inurl viewerframe mode motion network camera free