1. Unintended consequences

2. References

A cross-domain solution (CDS) is a means of information assurance that provides the ability to manually or automatically access or transfer information between two or more differing security domains.^[1] They are integrated systems of hardware and software that enable transfer of information among incompatible security domains or levels of classification.^[2] Modern military, intelligence, and law enforcement operations critically depend on timely sharing of information.^[3] CDS is distinct from the more rigorous approaches, because it supports transfer that would otherwise be precluded by established models of computer, network, and data security, e.g., Bell–LaPadula model and Clark–Wilson model.{{Citation needed|date=October 2012}} CDS development, assessment, and deployment are based on risk management.

The goal of a CDS is to allow an isolated critical network to exchange information with others, without introducing the security threat that normally comes from network connectivity.

The three primary elements demanded from cross domain solutions are:

1. Data confidentiality; most often imposed by hardware-enforced one-way data transfer
2. Data integrity: content management using filtering for viruses and malware; content examination utilities; in high-to-low security transfer audited human review
3. Data availability: security-hardened operating systems, role-based administration access, redundant hardware, etc.

The acceptance criteria for information transfer across domains or cross-domain interoperability may be simple (e.g.{{Citation needed|date=October 2012}} antivirus scanning before transfer from low to high security domains) or complex (e.g. multiple human reviewers must examine and approve a document before release from a high security domain^[4]).^[5] One-way data transfer systems (one-way traffic systems, data diodes),^[6][7] are often used to move information from low security domains to secret enclaves while assuring that information cannot escape.

Cross-domain solutions often include a High Assurance Guard.

To get a good foundation for Cross Domain Solution deployment, visit the DISA Mission Partners website and watch the following instructional videos:

• CDS 101 CBT (11 minutes)

• CDS CAP CBT (12 minutes)

• DSAWG 101 CBT (17 minutes)

Though cross-domain solutions have, as of 2019, historically been most typical in military, intelligence and law enforcement environments, there is also a use case for cross domain solutions in industry. Many industrial settings have control systems and analytic systems which are, or should be, in different security domains. One example is the flight control and infotainment systems on an airliner.^[8] Given the wide variety of use cases in industry, different levels of third party accreditation and certification of aspects of the cross-domain solution will be appropriate for different applications, and can be found among different providers.^[9][10]

Unintended consequences

In previous decades, multilevel security (MLS) technologies were developed and implemented that enabled objective and deterministic security, but left little wiggle room for subjective and discretionary interpretation.{{Citation needed|date=October 2012}} These enforced mandatory access control (MAC) with near certainty.{{Citation needed|date=October 2012}} This rigidity prevented simpler solutions that would seem acceptable on the surface.{{Citation needed|date=October 2012}} Automated information systems have enabled extensive information sharing that is sometimes contrary to the need to avoid sharing secrets with adversaries.{{Citation needed|date=October 2012}} The need for information sharing has led to the need to depart from the rigidity of MAC in favor of balancing need to protect with need to share.{{Citation needed|date=October 2012}} When the ‘balance’ is decided at the discretion of users, the access control is called discretionary access control (DAC) that is more tolerant of actions that manage risk where MAC requires risk avoidance.{{Citation needed|date=October 2012}} Allowing users and systems to manage the risk of sharing information is in some way contrary to the original motivation for MAC.

The unintended consequences of sharing can be complex to analyze and should not necessarily be left to the discretion of users who may have a narrow focus on their own critical need.{{Citation needed|date=October 2012}} These documents provide standards guidance on risk management:

1. {{cite web |url=http://csrc.nist.gov/publications/PubsSPs.html |title=Recommended Security Controls for Federal Information Systems & Organizations |date=2011-11-16 |work=Computer Security Division - Computer Security Resource Center |publisher=National Institute of Standards and Technology (NIST)}}, SP 800-53 Rev3
2. {{cite web |url=http://www.cnss.gov/Assets/pdf/Final_CNSSI_1253.pdf |title=Security Categorization and Control Selection for National Security Systems |work=The Committee on National Security Systems (CNSS)}}, Instruction No.{{Citation needed|date=October 2012}} 1253

References

Unified Cross Domain Management Office (UCDMO), Cross Domain Overlay, 1 December 2011, ver 1.0; provides extensive security control guidance to implement CDS platform address security controls for hardware and software, enforced with advanced inspections.

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