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.