Web caches, proxies, and translation services often appear as sites where Google Adsense has detected your ad code. Here is a list of services I’ve seen on my account:
For my properties, I primarily receive this message from the Adsense console due to translation services accessing the site and pulling my Adsense code through to their front-end. Generally, it is not a good idea to add translation services, caches, and proxies to your Adsense account. Although depending on the number of readers you have translating your site, you could gain a few extra percent of ad revenue. This does, however, come with some major risks which may outweigh the small percentage of revenue gain you could see from these new domains.
Within the Adsense Sites configuration [Adsense > Sites > Overview] you can control the list of sites your code appears on.
This feature was added as a way to protect your account from “malicious use of your ad code by others”. The sites in your sites list are the only sites that are permitted to use your ad code. If a site displaying your ad code is not on your list of sites, then no ads will show on that site.
Malicious use of your ad code could include generating false clicks on your site for the purpose of harming your Adsense account, revenue, and reputation. A malicious actor might include a competitor or someone else looking to harm your site for their own financial gain.
By enabling translation sites, caches, and proxies to display your ad code, you open your account be displayed alongside content you might not control. Malicious actors could serve up your ad code alongside restricted content creating negative marks on your Adsense account. Because Proxies are known to be couriers of less desirable internet content (and thus are disallowed by Adsense ToS), I would never risk adding a proxy domain to my AdSense account. Auto-translating sites are a risk as well due to the poor quality of the translations. In most cases, auto-translated content is considered low-quality by Adsesnse. Because caches are often a direct mirror of your content they carry a smaller risk of being low-quality or malicious, but for most, the risk likely doesn’t outweigh the payoff.