how to hide directory listings without breaking links

so, here’s what i’m trying to do: i want to use this plugin so that only authenticated users can view my site.

this works fine, but the directory listings, e.g. myblog.com/images/ is not affected by this measure. i’ve tried creating htaccess pw restrictions on those directories, but then the wp-authenticated users can’t gain access to those images.

(i previously had the whole website htaccess blocked but i find that to be a sad an annoying way of protecting my files.)

does anyone know what i can do? i’m not very familiar with htaccess and am just kind of hacking my way through this.