Found this digging in the forums, it was new news to me and thought others might not know either... so I thought I would place it here.

from DrByte:

Further, if you are careful to NEVER click a link to an external site (even via bookmarks or linkbars etc) while logged into your admin, then its existence won't be shared.
Remember, when you click on a link, the info about what site you're going FROM and going TO can be tracked by the servers involved. Thus, if you have your admin open and then open another site from your admin, you have just shared your admin URL with that other site's server, and it will show up in their stats reports.
So, the key is ... don't do that ! Always access your admin from a fresh browser tab/window, and always close it when done.
Then google and others won't be able to index it.

Its security is largely dependent on your safe-computing practices.
http://www.zen-cart.com/forum/showpo...77&postcount=7