I have no problem with legit ads. I realize these sites must earn some income or they won't be here.
I just hate these flashing, in your face things that do not identify who they are put up by. They can't be researched. at least not easily, to see if they are legit which means if you do click them, even inadvertently, you may have just downloaded a pile of garbage and opened the door to a whole pile more.
I just went through this. How I got it I don't know but I found out that the b++++++s double or even triple loaded files so even when I got rid of one there was another hiding elsewhere in the system to reload immediately or as soon as I fired up my m/c.
It finally fouled things up so I.E. wouldn't even start. Luckily I had Safari which did work, if not great it helped.
Even before that happened it seriously interfered with reading and opening T.F. and a few other sites. Banner ads, buried ads.
It took a lot of effort and some luck in finding some removal tools. I had to be very carefull though that I didn;t wipe out legit stuff essential to the computer.
So be very suspicious of stuff like this especially if the ad does not truly I.D. who it is so it can be Googled or researched otherwise.
Of course I'm travelling so it makes it harder to deal with this stuff.
These are two good places to read about and download various protection programs, free and paid. There are others of course where reading can be done.