What is Information Rights Management ?

Traditionally, sensitive information can be controlled only by limiting access to the networks or computers where the information is stored. After a user is given access, however, there are no restrictions on what can be done with the content or to whom it can be sent. Microsoft Information Rights Management (IRM) enables you to create a persistent set of access controls that live with the content, rather than a specific network location, which can help you control access to files even after they leave your direct control

With Windows SharePoint Services, IRM is available for files that are located in document libraries and stored as attachments to list items. Site administrators can elect to protect downloads from a document library with IRM. When a user attempts to download a file from the library, Windows SharePoint Services verifies that the user has permissions to the requested file, and issues a license to the user that enables access to the file at the appropriate permissions level. Windows SharePoint Services then downloads the file to the user's computer in an encrypted, rights-managed file format.