When it comes to the subject of privacy, more options are usually better. Bloggers and members of your site are more likely to trust and recommend your community if they know that they have the option to protect their content.
WordPress Multisite Privacy Settings
By default, WordPress Multisite has two site visibility settings under the Settings >> Privacy menu, both related to search engines:
Allow search engines to index this site
Ask search engines not to index this site
If you want more privacy options, it’s as easy as installing a plugin.
WordPress Multisite Plugin: More Privacy Options