The Bamboo Column Level Security column encrypts text, numeric, and currency based data, allowing only users and groups designated by the list owner to see the contents of the column.
With column level security, you can store secure and public data side by side, knowing that each user will only be shown data they have access rights to. Even better, you can individually and independently assign read/edit access, so data can be viewed, but not edited, by mid-level users.
Best of all, the Bamboo Column Level Security column even lets you easily copy
existing data into a new, secure column, making it easy to add customized security to
the SharePoint data you already have.