Blocking access to uploads in Multisite


I'm running a site on a Multisite installation that is restricted to logged-in users. However if people have the direct url to a media file they can access it via the uploads directory for that site.

I don't have any membership plugins installed, just the Force User Login plugin.

All the solutions I've seen for this involve edit ing the .htaccess file which won't work for me as I need public access to uploads in other sites on the network.

Do you know of a solution to this that doesn't involve editing the settings for each media file as I upload it, but can let me restrict access to everything in the uploads folder for that site?