Read reviews of the Password Protected Categories plugin by Barn2.
Rated 4.78 out of 5 stars
Based on 23 customer reviews.
I had a very simple need for a photographer's website where the photographs are uploaded as featured images on posts -- create a private password-protected section for some photographs. So we created a category, put those photos in posts in that category and used this to protect the category and those posts. I could have written it myself but this was cheaper (and much faster!). Honestly, a few clicks and it was set.
