Most of the popunder ads do spread cookies as it stops them from opening up again and again. Using cookies in your popunder ads helps you to recognize if the individual has seen the ad before or not. If yes then the cookies prevents the ad from appearing on an individual’s computer again and again. If you don’t add cookies to your ad then it is possible that the ad would open up again and again and can turn out to be annoying. In this case the user might block the ad and this would make it impossible for you to reach out to them. This is why using cookies in the ad is important.
The cookies used in the ad are stored at a specific location on the user’s computer. So before the ad appears on a system, it looks for the cookie in it. If it finds the cookie then the ad doesn’t open but if not then it indicates that the ad hasn’t appeared on the particular user’s computer. The ad then comes up on his screen and the cookie is saved in his system. In case the user decides to delete the cookie then the ad might appear on the system again. The cookies are thus useful and is especially apt for the per user advertisement mode.