I had a similar experience not too long ago. When I logged into the Rogers forum, I got a Rogers survey request, and I participated. After I went through the survey, I was suddenly bombarded with ads that took up a lot of real estate on my screen. No matter what I did, I couldn't get rid of them. Scrolling down pages just resulted in the ads following down. I went into my browser settings (IE 11) and looked at my add-ons and, sure enough, there was one which I had never seen before. It was called something like realdeals and it was responsible for inserting the ads. I believe I got the add-on from downloading something from a site which, unknowingly, installed the add-on in addition to the item I wanted. I've never understood why browsers allow add-ons to be installed without permission. I looked at its settings and didn't see anything that would stop it. I realize I may be missing something, though.
I uninstalled realdeals, deleted it from my add-ons, and went through my registry to delete its entries. That solved the problem, but it was a real pain. After that, I did some searching and discovered this is a common problem. There are lots of web sites that show up when you're searching to download something. The lesson I learned is to be very careful and pay close attention to the web site URL when downloading things. Now, I always look for the site which belongs to the company that owns the software.
I also discovered that these things are call PUPs, which stands for something like Possible Unwanted Programs. I use Norton 360 which protects my system, but it does not recognize PUPs as being a problem. Then I discovered that Malwarebytes gets rid of them, so I downloaded the free version and run it every once in a while. It caught a few which were already on my system and got rid of them.
