How Do You Protect Servers From a Rogue Admin?

Treborto writes "I work with a non-profit that has an extensive collection of photos and videos. These are used in publications and on the web. We have several levels of privileges: read-only of small, watermarked images; read-only of large, clean images; edit of the site; and admins who can confer privileges. It has happened that people leave the organization in anger. So far, no Admin has done so. Is there a back-up, site mirroring, privilege, or other strategy you'd recommend so we have protection from an Admin gone bad?"