Here’s a nice plugin for securing some of your files.
This plugin allows you to upload and download documents that are stored outside of your web document root for security purposes.
This is great for people using plugins like Registered Only that secure your WordPress blog (Posts, Pages, etc). The problem with these plugins is that your loose files aren’t protected – only the contents of your WordPress database. So, any images or other documents you’ve uploaded are easily accessible to those who aren’t authenticated via a plugin like Registered Only. This plugin aims to solve this problem.