High Assurance Guard

A High Assurance Guard (HAG) is a Multilevel security computer device which is used to communicate between different Security Domains, such as NIPRNet to SIPRNet. A HAG is one example of a Controlled Interface between security levels. HAGs are approved through the Common Criteria process.

Operation

A HAG runs multiple virtual machines or physical machines - one or more subsystems for the lower classification, one (or more) subsystems for the higher classification. The hardware runs a type of Knowledge Management software that examines data coming out of the higher classification subsystem and rejects any data that is classified higher than the lower classification. In general, a HAG allows lower classified data that resides on a higher classified system to be moved to another lower classified system. For example, in the US, it would allow unclassified information residing on a Secret classified system to be moved to another Unclassified system. Through various rules and filters, the HAG ensures that data is of the lower classification and then allows the transfer.