Is there a way to secure upload files?

Okay so I was wondering if there is a way to protect the upload directory automatically when a blog is provisioned. When a blog is provisioned a folder is created in the blogs.dir and when the user uploads media that file is open for anyone to access directly. So if somebody is digging around in your source code they can see the entire url to lets say an image and they can simply remove the image file from the url and access the directory and parent directories. So I know that I can add an index file to each directory but is there a way to automate this. Or is there a better way to protect each users uploads directory. Thanks