WALTHAM, Mass.--(BUSINESS WIRE)--Digital Guardian, the only endpoint security platform purpose built to stop data theft, today announced its membership in the HP ArcSight Marketplace, a new online enterprise portal that unifies HP ArcSight® security content, products, documents and best practices. As one of the first partners to join the Marketplace, Digital Guardian will offer the new Digital Guardian Advanced Content for HP ArcSight, which enables customers to harness the security intelligenc