One of the unspoken challenges with OneNote is when it comes to security. By definition, the tool is designed for open collaboration. Unfortunately this can introduce a plethora of issues around protecting content and access to that content. Let's address some of the most common questions:
Can I protect content in OneNote using OneNote?
Unfortunately the only way currently to protect specific content within a OneNote notebook is from the desktop application and this is by applying a password at the Section level. You cannot protect individual pages nor can you protect specific notebooks. Honestly it's a strange level to apply password protection but that's where it is and we're stuck with it. Keep in mind these passwords are not recoverable nor do they cover multiple sections.
Can I share a notebook in Read Only mode?
Yes, you can share a notebook with someone else in read only mode. Just go to File > Share > Share with People. Enter the email address of the people you want to share the notebook with and then select "Can View" from the drop down, add your own message, and send it on it's way.
Can I protect a notebook using SharePoint?
SharePoint treats a OneNote notebook in the same way it would any other file. Your best practice to protect one or more notebooks in SharePoint is to put them in a SharePoint document library and then set the permissions on the library accordingly. OneNote creates a number of secondary files and folders when in use, so protecting the main notebook by itself can yield some unpredictable results.
How do I protect an archival notebook?
This requires a couple of steps but in the end you'll wind up with a secured copy of your notebook. First export the notebook using the desktop application as a OneNote package. Now using a compression tool such as WinZip compress the package and apply a password to the compressed file. Keep in mind the contents are not searchable without extraction, but you can put this ZIP file away and be able to retrieve it later with it's password protected contents.
So OneNote really isn't a secure tool?
Not in the traditional sense. Let's keep in mind it's designed to focus on collaboration and sharing and defaults to that thinking in just about everything it does. I can imagine over time Microsoft will expand the security capabilities of the tool but for now plan ahead and think carefully about what content you're placing in OneNote.