Networks connected to one-way (uni-directional) gateways implement diodes in order to protect the higher classified system.

]]> This section covers information relating to filtering requirements for one-way gateways used to facilitate data transfers.  Additional information that also applies to topics covered in the section can be found in:

]]> Further information on the Evaluated Products List can be found at:

Reference Title Publisher Source
  Evaluated Products List (EPL) AISEP https://www.cyber.gov.au/acsc/view-all-content/epl-products
]]> A diode enforces one-way flow of network traffic thus requiring separate paths for incoming and outgoing data.  As such, it is much more difficult for an attacker to use the same path to both launch an attack and release the information.  Using diodes of higher assurance levels for higher classified networks provides an appropriate level of assurance to agencies that the specified security functionality of the product will operate as claimed.

]]> Agencies MUST use devices as shown in the following table for controlling the data flow of one-way gateways between networks of different classifications.

High network Low network You require
RESTRICTED   UNCLASSIFIED EAL2 or PP diode
RESTRICTED EAL2 or PP diode
CONFIDENTIAL   UNCLASSIFIED high assurance diode
RESTRICTED high assurance diode
CONFIDENTIAL high assurance diode
SECRET   UNCLASSIFIED high assurance diode
RESTRICTED high assurance diode
CONFIDENTIAL high assurance diode
SECRET high assurance diode
TOP SECRET   UNCLASSIFIED high assurance diode
RESTRICTED high assurance diode
CONFIDENTIAL high assurance diode
SECRET high assurance diode
TOP SECRET high assurance diode
]]> As NZEO networks are particularly sensitive additional security measures are necessary when connecting them to other networks.

]]> Agencies MUST use a diode of at least an EAL4 assurance level between an NZEO network and a foreign network in addition to the minimum assurance levels for diodes between networks of different classifications.

]]> In all other circumstances the table at 19.4.4.C.01 MUST apply.

]]> Agencies SHOULD use a diode of at least an EAL2 assurance level or a Protection Profile between an NZEO network and another New Zealand controlled network within a single security domain.

]]> Monitoring the volume of data being transferred across a diode will ensure that it conforms to expectations.  It can also alert the agency to potential malicious activity if the volume of data suddenly changes from the norm.

]]> Agencies deploying a diode to control data flow within one-way gateways SHOULD monitor the volume of the data being transferred.

]]>