Password Protected Area

I have an area on my wordpress site which I would like to protect but I don’t want to use the standard password protection that WordPress provides as I could have a lot of pages within the area. So for example…

I have a category of /portfolio that I would like to protect that and then any posts that are also within that area of the site.

I’ve tried doing this with htaccess but it either doesn’t work or breaks the site!

Any ideas or help would be greatly appreciated.