A secure blog is a blog that is password-protected. Bloggers who only wish to share information with people they know choose to have a private blog.
To make your blog password secured, go to the "Configure" section, then to the "Global options" tab and click "Security" in the left-hand side column.
User's guide
Private blog / restricted-access blog / secure blog
Terms : private blog, private blogs, password protected blog, restricted-access blog, secure blog, family blog...