You can check for free what other sites a person has if you have is Adsense number. Is there a way to block this? Sometimes i have Adsense on customer sites and not mine and in different categories i do not want to tell the competitors.
I think there is no way because you can not hide your adsense id, and if so, you can not hide your other sites. What you can do is blog the bots who scrolls for adsense id. May be this may work.
I don't think your AdSense ID is also detectable on SpyOnWeb. I put in my website on SpyOnWeb and it detects my AdSEnse ID but can't find the other websites with the same AdSense ID
Get to the source of the problem: Never, EVER, tell anyone your Adsense sites. If you do, it's very easy for them to find the rest of your Adsense sites.
Yes, it's not possible because adsense publisher id is public, it is in the html source code of any place where you put it.. So you only have to find sites dedicated to that, like spyonweb in order to know more about one's websites.. But honestly, I don't see why you want to hide it, just focus on your own work and let the lamers copy, they'll get nowhere and you'll always be way ahead..
It is not about that it is more about i do not want them to see what other websites i have. I guess i can open one company one website but will drive the accountants nuts
If you are worried about your ads being on other sites just turn on your "allowed sites" and enter your sites in the list. https://www.google.com/adsense/publisher-whitelist-view
yes, you can open another adsense account, that's your only solution, but beware also not to use the same google analytics account, not the same web server (ip) and other things which could be identical on all your sites.. The best is just to ignore the copy and let the people who want to spy on you, do it.. If they are spying it means they'll go nowhere, you'll always be ahead as long as you don't waste time thinking about it.