Cytherian probes were devices built by the Cytherians to seek out other races and bring them to their homeworld. A probe attempted contact with the Argus Array in 2367 and then attempted to reprogram the USS Enterprise-D's computers. The probe was able to reprogram Lieutenant Reginald Barclay's brain to bring the ship to the Cytherian homeworld. (TNG: "The Nth Degree")