For a while I have been experiencing online ads that are not legitimate and are targeted at me personaly. Usualy they are ad images that are placed in ad slots but don't appear to be genuine. Recently I have experieced the same thing with youtube video ads. Ads that interupt a long video. I think it's aimed at me, not random. I don't think this is normal target advertising. If I'm able to visit sites using Tor it doesn't happen. I would like to know how this is possible? What is the likely method being used? How would someone be able to place a video ad on youtube? I read somwhere that an image can be replaced with a "man in the middle" attack? Is there anything I can do to find out the cause?