The former Director of Central Intelligence Directives 6/3 established specific protection levels based on an information system’s assessed level of concern. In 2008 The Office of the Director of National Intelligence (ODNI) began releasing Intelligence Community Directives (ICD) that were to eventually supersede the DCID. I’m no longer an active practitioner of Certification and Accreditation so it is unclear to me whether the ICD 500 series has actually superseded or cancelled the DCID 6/3. From my interactions over the past 18 months I’m thinking that the DCID 6/3 is still alive combined with specific ICD 500 guidance and 800-53. Regardless, in my opinion the DCID 6/3 offers some great legacy guidance for multi-tenant clouds.