"ViewerFrame?Mode=" is a Google search string that can be used to find Internet-connected security cameras and other webcams. While some of those are intended to be public, others are private cameras, making these searches a potential security problem.
Many companies and private individuals use IP-based techniques to access cameras remotely; for example, they can be used to view a network of security cameras from an office. This practice saves costs compared to a cable connection, but also inadvertently makes the cameras accessible from the Internet and visible to search engines.
Cameras often have "viewerframe?mode=refresh" or "viewerframe?mode=motion" in their URLs. Other search strings can be used in similar fashion. The location of the camera, specifically the country and city can then be determined by a domain search. Sites such as Insecam collect this information and provide streams from a large number of publicly accessible cameras. They may remove a camera from their directories on request from the camera's owner.
If a camera is unprotected, it can sometimes even be controlled remotely. Some cameras are protected by password login, but hacking software and techniques can bypass these protections. Specialized programs secure cameras further by coding the video stream or making it accessible only from designated IP addresses.