Abstract: A system and method for controlling the security of data in a central high speed data processing unit (CPU) by electronically sensing and comparing all operating or control statements coming into the CPU from terminal devices with a vocabulary of all statements unacceptable for security reasons which unacceptable statements are stored in a remote secondary computer system. The security of the data is also controlled by electronically sensing and comparing all operating and problem steps loaded into the CPU from library devices with a collection of identifiers known to identify all correct versions. The reaction to security dangers found in either sensing and comparing method is to exert predetermined counteraction to preclude unauthorized removal, alteration, destruction or inspection of problem data and/or procedures.The system includes a plurality of sensors which monitor operating control statements, operating and problem steps or procedures and physical switches on the CPU control panel.