ASD ISM 0645 High assurance evaluation of unidirectional gateways
What it says
Evaluated diodes used for controlling the data flow of unidirectional gateways between SECRET or TOP SECRET networks and public network infrastructure complete a high assurance evaluation.
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What it means
In plain EnglishEnsure diodes used between secure and public networks are highly evaluated for safety.
This control is about making sure that devices called diodes, which control which direction data can flow across a network, are thoroughly checked for safety when connecting high-security networks to public ones. This matters because if these diodes fail or aren't properly evaluated, sensitive information could leak out from a secure network, leading to serious breaches of privacy and security.
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Why it matters
Using non-evaluated diodes in unidirectional gateways can allow data exfiltration from SECRET/TOP SECRET networks to public infrastructure, causing compromise.
How to implement
Security managers should ensure that any network diodes intended for use between secure and public networks undergo a high assurance evaluation.
This involves checking the certification or evaluation reports from reputable security organisations, such as the Australian Cyber Security Centre (ACSC).
IT teams should establish contracts with suppliers that outline the specific safety evaluations required for diodes.
They can do this by specifying that the devices must meet certain standards and come with documented proof of evaluation.
System owners should collaborate with network administrators to perform regular tests and checks on the diodes in use.
They can do this by setting a schedule for testing device functionality and logging any maintenance or incidents.
Procurement officers should only purchase diodes from vendors with a strong track record of high assurance evaluations.
They should request and review case studies or references that confirm the vendor's compliance with strict security evaluations.
Compliance officers should keep records of all evaluations and certifications related to the diodes used.
They can ensure this by maintaining a secure, organised repository that archives all documentation and correspondence related to these evaluations.
Keep it running
Confirm the diode model and version used in the unidirectional gateway retains current high assurance evaluation, and record certificate IDs, scope and expiry in a review log.
Evidence and audit
- Check 1 of 5What an auditor asks for
Ask for
The diode evaluation reports: Request the documented evaluations that confirm the diodes used between networks meet high assurance standards.
Look at
The evaluation date and certifying body's details.
Good evidence
Reports show recent evaluations by reputable bodies like ACSC or ASD (Australian Signals Directorate).
- Check 2 of 5What an auditor asks for
Ask for
The procurement contracts with diode vendors: Request the contracts to verify they stipulate safety evaluation requirements.
Look at
Clauses specifying assurance evaluations as a condition.
Good evidence
Contracts include detailed evaluation criteria before purchase is approved.
- Check 3 of 5What an auditor asks for
Ask for
Diode testing schedules and logs: Request documents that show regular testing and maintenance of diode functionality.
Look at
Consistent intervals and any logged incidents with resolutions.
Good evidence
A clear schedule with logs documenting tests, findings, and any actions taken.
- Check 4 of 5What an auditor asks for
Ask for
Vendor compliance documentation: Request proofs, like certification or references, demonstrating the vendor's adherence to high assurance standards.
Look at
The credibility of the certifying entities and recent compliance proof.
Good evidence
Current certificates and positive references from known security organisations.
- Check 5 of 5What an auditor asks for
Ask for
The repository of evaluation documentation: Request access to the storage system where evaluation documents are kept.
Look at
Organised, up-to-date files that are easy to navigate.
Good evidence
An orderly digital folder with searchable, well-labelled files by date and diode type.
Mappings
Closest match in ISO/IEC 27001: A.8.22, Network segregation for security, which this control partially meets.
ISO/IEC 27001: 1 mapping
This control partially meets A.8.22.
ISM-0645 requires high assurance evaluation of evaluated diodes used in unidirectional gateways at SECRET/TOP SECRET to public network boundaries to provide strong one-way separation. Annex A 8.22 requires network segregation of information services, users and systems, and at highly sensitive boundaries one-way gateways are one possible (though not required) segregation mechanism. ISM-0645 is narrower because it specifies a particular cross-domain segregation implementation and an assurance level for the diode, whereas Annex A 8.22 remains technology-agnostic and broader in scope.
Mappings show how controls relate across frameworks. They do not imply full equivalence or certification.