Data diodes are devices used to provide secure, one-way data transfer between two networks. High security networks, such as some government, defense, manufacturing, and critical infrastructure networks (energy, water supply, etc.) are often disconnected from the Internet in air-gapped or isolated networks.
Using isolated networks is very effective for security but can hamper efficiency and are usually costlier to operate. In order to improve productivity, and reduce costs while maintaining security, data diodes can be used to provide one-way traffic into the secure network, ensuring that data can enter the network, but no data can leave.