What is Cross-domain solution?

A cross-domain solution is an integrated information assurance system composed of specialized software, and sometimes hardware, that provides a controlled interface to manually or automatically enable and/or restrict the access or transfer of information between two or more security domains based on a predetermined security policy. CDSs are designed to enforce domain separation and typically include some form of content filtering, which is used to designate information that is unauthorized for transfer between security domains or levels of classification, such as between different military divisions, intelligence agencies, or other operations which critically depend on the timely sharing of potentially sensitive information.

The goal of a CDS is to allow a trusted network domain to exchange information with other domains, either one-way or bidirectionally, without introducing the potential for security threats that would normally come with network connectivity. Although the goal is 100% assurance, this is not possible in practice, thus CDS development, assessment, and deployment are based on comprehensive risk management. Due to the sensitive nature of their use, every aspect of an accredited CDS must be rigorously evaluated under what is known as a Lab-Based Security Assessment in order to reduce the potential vulnerabilities and risks to the system itself and those to which it will be deployed. The evaluation and accreditation of CDSs in the United States is primarily under the authority of the National Cross Domain Strategy and Management Office within the National Security Agency.

The three primary elements demanded from cross domain solutions are:

The acceptance criteria for information transfer across domains or cross-domain interoperability is based on the security policy implemented within the solution. This policy may be simple check before transfer between peer networks] or complex. Unidirectional networks 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.