Technologies such as firewalls and ACLs allow you to restrict access to digital information, but such perimeter-based solutions are limited in the protection they can offer. Microsoft's Windows Rights Management Services (RMS) is designed to supplement those measures by offering persistent security that stays with a file no matter where it goes.
RMS consists of two primary components: the RMS service itself, a server level component that provides the authentication services, and the client component. Typically, the client component is embedded into an RMS-enabled application such as Microsoft Office 2003. A software developer's kit allows developers to build RMS security into custom applications as well.
The Microsoft white paper Windows Rights Management Services for Windows Server 2003: Helping Organizations Safeguard Digital Information from Unauthorized Use explains the mechanics of implementing Windows Rights Management Services. The paper includes a discussion of the need for this type of technology, an introduction to RMS components, a look at various deployment options, and an appendix that covers the RMS interoperability standard, XrML.