Computers at Marin Healthcare District's nine medical care centers were hit with a virus that holds data hostage but officials are not discussing details. A ransom was paid to regain access to the data, according to the Marin Independent Journal, but requests for further comments from Marin Medical Practices Concepts, Inc., the Novato-based company that provides the district with business and health care system services, went unanswered. Security reasons were cited.