Originally Posted by asorelli

This plugin appears to do just that:

Hotlink File Prevention (HFP) plugin
One notable option is the Hotlink File Prevention (HFP) plugin. This plugin enables you to protect individual files in your WordPress media library from hotlinking by leveraging .htaccess rules in the wp-content/uploads directory. It adds a "Hotlink Protection" checkbox when editing individual media files, allowing you to easily enable or disable this feature for specific items.

Edit (Added)
There may be others as well, so do your own research. This is not a replacement for the plugin that Marshal created, just an additional layer of protection since a couple people were concerned about users being able to open up big images and not being blurred. I also have no idea if the plugin works for new versions of wp, or will cause any conflicts with your site -- use at your own risk.