All Behance profiles are visible to the public, so unfortunately this is not an option. You can restrict the ability to view projects by changing the privacy options in the project itself, but your profile still will be searchable via search engines. 

To restrict access to any project:

1. Click on the Project
2. Navigate to the Project's Settings
3. Click Edit next to Projects visible to -->turn all OFF

* Note:

1. You can give certain Behance members of your choice access to restricted projects in Limit Visibility, but there is not password protect option for the general public.
2. Adobe Portfolio gives you the ability to password protect any page of your choice or the full website. This will allow you to share your private projects or site with clients, or anyone else you give the site password to.