Fixing the holes is not easy as the hackers use packet sniffers /virtualization to claim ownership of the website.
It is your responsibility to do the work to secure your site or you could have FAR worse problems than a little lost ad revenue.
If hackers are able to place ads on your site, they are also able to place anything on your site, divert your traffic, infect your visitors (and your) machines. When that happens your site gets removed from the index and you can read many sad stories from others about how much trouble that is.
It does not matter how your site was compromised, it is up to you to fix the problem. Read here on the forum, use the Search, ask for help with the real issues and you can fix this problem at the same time.