Borg data node
Data nodes were portable storage and processing devices utilized by the Borg to archive and transfer information. Multiple ones would be used on a ship to store data on its drone manifest and tactical information, such as long-range sensor telemetry, assimilation logistics, and other starship movements. (VOY: "Drone", "Dark Frontier")
In 2375, the 29th century Borg drone known as One was given Borg data nodes by Seven of Nine from which to assimilate information as she deemed that a direct neural interface was too dangerous. (VOY: "Drone")
Later in 2375, the crew of the USS Voyager managed to salvage several data nodes from the remains of a destroyed Borg probe, aiding in the eventual theft of a transwarp coil, in Operation Fort Knox. (VOY: "Dark Frontier")