First of all, they are not IBO member ads. These are ads that are being shown from Google.
Here is a snippet from Google:
As users browse our partner websites, Google stores an advertising cookie in a user's browser to understand the types of pages that user is visiting. This information is used to show ads that might appeal to your users based on their inferred interest and demographic categories.
For example, if a user browses many sports-related websites displaying AdSense ads or watches sports-related videos on YouTube, Google may associate a sports interest category with their cookie and show the user more sports-related ads. Similarly, if the sites that a user visits have a majority of female visitors (based on aggregated survey data on site visitation), we may associate the user’s cookie with the "female" demographic category. We may also use demographics from Google profiles.
Users can edit their inferred interest and demographic categories within Ads Settings.
For more information about Google ads: