Topic

Separation of data flows

Applicable to

Secret, Top Secret

History

Priority

Must

Mar 2022

CDSs implement protocol breaks at each network layer.

Miscellaneous changes were made to rationale and recommendations throughout the publication to clarify content without changing intent. This included a review from the Guidelines for System Hardening chapter through to the Guidelines for Data Transfers chapter.

Dec 2021

A CDS implements protocol breaks at each layer of the OSI model.

Miscellaneous changes were made to rationale and security controls throughout the publication. This included:

• A review from the Using the Information Security Manual chapter through to the Guidelines for Media chapter.

• Security controls suitable for all audiences have been identified with the ‘All’ applicability marking while additional security controls suitable for just government audiences have been identified with the O, P, S and TS applicability markings.

• Security controls suitable for specific classifications have been amended to include their classification(s) in the wording of the security controls to reduce the reliance on applicability markings to confer suitability.

• Tables in security controls have been converted into prose to allow for inclusion in the SSP annex template and the XML list of security controls.

• The use of ‘official’ and ‘highly classified’ terminology has been replaced with specific classifications to remove ambiguity.

• Security controls relating to high assurance ICT equipment have had their applicability narrowed to ‘S, TS’ reflecting that they are intended for the protection of SECRET and TOP SECRET systems and data.

Dec 2019

A CDS between a highly classified network and any other network implements protocol breaks at each layer of the OSI model.

Security controls 0635, 1521 and 1522 were modified slightly to reflect the use of CDS as singular rather than plural.

Nov 2019

All CDS between highly classified networks and any other network implement protocol breaks at each layer of the OSI model.

Nov 2018

All CDS between highly classified networks and any other network implement protocol breaks at each layer of the OSI model.

Added to address a gap in guidance on the separation of data flows in Cross Domain Solutions (CDS).