Network interface circuitry for a secure one-way data transfer from a sender's computer (“Send Node”) to a receiver's computer (“Receive Node”) over a data link, such as an optical fiber or shielded twisted pair copper wire communication cable, comprising send-only network interface circuitry for transmitting data from the Send Node to the data link, and receive-only network interface circuitry for receiving the data from the data link and transmitting the received data to the Receive Node, wherein the send-only network interface circuitry is configured not to receive any data from the data link, and the receive-only network interface circuitry is configured not to send any data to the data link. The network interface circuitry may use various interface means such as PCI interface, USB connection, FireWire connection, or serial port connection for coupling to the Send Node and the Receive Node.