thirteen - 1:34 am on Feb 17, 2012 (gmt 0)
1) View the source page to check for <iframe></iframe> tags. If it is there, that's how they pull your website content.
2) Login to your Adsense Account, Account Settings and enable Access and Authorization. Define which sites are authorized to show ads. Your Adsense Account is vulnerable to be canceled through no fault of yours if you don't protect it with this setting.