Abstract: Multilevel secure network access system. A workstation can access information having two or more different security classifications stored on servers within networks. Servers of one security classification are isolated from servers of another security classification by each type of server being disposed within its own isolated network or network segment. A switching unit controls input device access from a workstation. Data diodes between the networks in combination with proxy software located within each network keep data isolated. The viewing of information from at least some of the networks is accomplished through so-called “thin” or “ultra-thin” client software installed on the workstation. The use of such an ultra-thin enclave client minimizes the amount of data stored on the workstation and therefore any commingling of data of different security levels at the workstation. It also allows commercial off-the-shelf (COTS) software to be used without modification.