ASD ISM 1158 High assurance evaluation for network diodes
What it says
Evaluated diodes used for controlling the data flow of unidirectional gateways between SECRET or TOP SECRET networks and any other networks complete a high assurance evaluation.
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What it means
In plain EnglishDiodes ensure secure, one-way data flow between secret and other networks.
This control is about ensuring that any special equipment called a 'network diode' used to send information in one direction between highly secure networks and other networks has been thoroughly checked for security. This matters because without these checks, sensitive information could accidentally or maliciously leak into less secure areas, leading to serious security breaches.
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Why it matters
If a diode lacks a high assurance evaluation, unidirectional gateways may fail, enabling data leakage from SECRET/TOP SECRET networks to lower domains.
How to implement
The IT manager should select a secure network diode that meets high assurance security standards.
They can do this by reviewing evaluations and certifications from reliable security assessments, such as those recommended by the Australian Cyber Security Centre (ACSC).
Systems administrators should install the network diode between the secure and less secure network environments.
This involves physically connecting the diode and ensuring that it is configured to allow data transfer only in the designated direction, preventing reverse data flow.
The IT security team should conduct regular checks and tests on the network diode to confirm it is functioning correctly.
This can be done by monitoring data transfer logs and ensuring no data flows in the wrong direction.
Procurement officers should document the acquisition process of the network diode, ensuring that all vendor claims about its security capabilities are verified.
This involves retaining certificates, evaluation reports, and references to confirm the product meets the required security standards.
The management team should organise training sessions for staff to understand the role and importance of the network diode in organisational security.
This includes explaining the consequences of data leaks and how the diode helps prevent them.
Keep it running
Use only network diodes that have completed high assurance evaluation; confirm model/firmware against evaluated product lists and re-check status after upgrades or replacements.
Evidence and audit
- Check 1 of 5What an auditor asks for
Ask for
The diode evaluation report from the vendor: Request to see the document that details the security checks done on the diode.
Look at
Clear criteria of assurance levels and passed evaluations.
Good evidence
Will include a recent, dated report showing successful evaluations against known standards.
- Check 2 of 5What an auditor asks for
Ask for
The installation and configuration records: Request documents detailing how the diode was set up.
Look at
The details of installation and any diagrams showing placement.
Good evidence
Is a record showing correct installation with diagrams confirming the one-way data flow.
- Check 3 of 5What an auditor asks for
Ask for
Regular test logs: Request records of ongoing tests verifying diode functionality.
Look at
The frequency and results of these tests.
Good evidence
Includes consistent logging with no failures in data directionality over several test cycles.
- Check 4 of 5What an auditor asks for
Ask for
The training materials used for staff: Request to see any presentations or guides on diode function.
Look at
Easy-to-understand materials that cover diode function and importance comprehensively.
Good evidence
Includes complete training content with attendance records for staff.
- Check 5 of 5What an auditor asks for
Ask for
Records of procurement processes: Request copies of procurement validation checklist.
Look at
Checks against high assurance requirements and verification documents from third parties.
Good evidence
Is a checklist signed off by competent authorities verifying compliance.
Mappings
Closest match in ISO/IEC 27001: A.8.20, Network and network devices security, which this control partially meets.
ISO/IEC 27001: 2 mappings
This control partially meets A.8.20.
ISM-1158 requires that network diodes used to enforce one-way data flow in unidirectional gateways between SECRET/TOP SECRET networks and any other networks have completed a high assurance evaluation. Annex A 8.20 requires networks and network devices to be secured, managed and controlled, which includes selecting appropriate security-enforcing network components and assuring they are fit for purpose. ISM-1158 is a highly specific assurance requirement for a particular network device and classified cross-domain scenario, while Annex A 8.20 is a broad control covering network/device security generally.
This control partially meets A.8.22.
ISM-1158 requires high assurance evaluated network diodes for unidirectional gateways separating SECRET/TOP SECRET networks from other networks. Annex A 8.22 requires segregation of groups of information services, users and systems within organisational networks, and unidirectional gateways are one concrete mechanism used to achieve strong segregation where one-way flows are required. The candidate control does not require diodes or evaluation, but ISM-1158 strengthens the segregation outcome by mandating assurance of the component that enforces the separation.
Mappings show how controls relate across frameworks. They do not imply full equivalence or certification.