SOX was a name of a UNIX clone developed from scratch in Brazil in late 1980s by Computadores e Sistemas Brasileiros S/A (now Cobra Tecnologia), under the leadership of Ivan da Costa Marques. Certified as UNIX-compatible by X/Open (through Unisoft) in early 1989, SOX was one of the first re-implementation of UNIX fully independent of AT&T that passed the X/Open verification tests, and the only one ever completed 100% outside the United States.
SOX was designed to run on COBRA's own minicomputers and was part of Brazilian Informatics Policy that aimed to achieve technological independence from the United States. Despite being a technical success, SOX came too late, when COBRA had largely lost its support. SOX development was stopped soon after it was certified when the government decided to instead allow import of UNIX System V Release 4.0.