Ads taking over TV screen

During the past week, while watching TV, the screen will stop showing the program video and instead will display a single screen advertisement for a website or local store. I can bring up the menu or guide, but after exiting the same screen remains. Sound continues for the program. The only way to get the ad off is to change channel and return to the channel you were trying to watch. It is like a pop-up ad virus took over the cable TV. Is this a new ad setting? How do I remove it?