It happens even to an experienced user like me that on a slow connection I tend to click "Admin" and "Host" in Control Panel to speed up opening of the menu - and get redirected, waiting again for the menu page to open. if you want to disable both root items, you may enter Pages item in Host menu, right click on Admin menu root item and select disable, as well as switching to system menu and perform same for Host menu root item (or run
UPDATE {databaseOwner}[{objectQualifer}Tabs] SET disableLink = 1 WHERE TabPath Like '\\Admin' or TabPath Like '\\Host'
in Host > SQL and restat application).
When moving back to home page, you will notice that clicking either item will no longer forward you to the menu pages - however, it does no longer open menus as well. To fix this behaviour, download this XSLT file and place it into \admin\Menus\DNNAdmin folder, overwriting existing file. Now, Admin and Host item will open the menu, but not taking you to the disabled menu pages.