Abstract: The invention relates to an apparatus which enables, via an elementary manipulation, protection against access to and destruction of data contained in a computer system or deactivation of such protection. The protected computer system may include a housing of a central processing unit (CPU) with its memories, the housing being separate from data access devices. The CPU and memories are connected to the data access devices by connectors which are external to the housing. The housing is defined by an enclosure (18) provided with at least one door or the like. Advantageously a plurality of housings may be defined in the enclosure, each of which housings can benefit from the inventive apparatus. Closing of the door causes a multipolar switch (28) to open, which switch is electrically connected between:links connected to the data access devices located outside the housing;connectors of/from the housing which connectors are to be protected.