Controlled interface

A controlled interface is a multilevel security system used to transfer low-classification data between security domains. The data to be transferred may theoretically move in either direction; the purpose of the controlled interface is to ensure that the data meets the criteria for transfer. This normally means that the data is of the lower classification. One example is the High Assurance Guard.

The Committee on National Security Systems (CNSS) publishes the 'NATIONAL INFORMATION ASSURANCE (IA) GLOSSARY', also known as CNSS Instruction No. 4009. In this glossary, a Controlled Interface is defined as follows: "Mechanism that facilitates the adjudication of different interconnected system security policies (e.g., controlling the flow of information into or out of an interconnected system".

While some controlled interfaces are very complicated, others are very simple. A simple example of a controlled interface is a one-way data transfer system that moves data from a low security network to a high security network while assuring that high security data can never escape. One-way controlled interfaces are also called data diodes.