ALTHOUGH THE NETWORKING OF LARGE ADP AYSTEMS, WITH ALL ITS ATTENDANT BENEFITS, IS BECOMING INCREASINGLY COMMON, CARELESS NETWORKING CAN RESULT IN SECURITY PROBLEMS. NETWORK DESIGN CAN EITHER INTENSIFY OR REMEDY SECURITY PROBLEMS. CAREFUL NETWORK DESIGN MUST INCORPORATE FUNDAMENTAL SECURITY PRINCIPLES, THE MOST ESSENTIAL OF WHICH IS THE INCORPORATION OF A SECURITY REFERENCE MONITOR WHICH CHECKS ALL COMPUTER INQUIRIES. MILITARY COMPUTER SYSTEMS FACE THE FUNDAMENTAL PROBLEM OF DEVELOPING EFFECTIVE MULTI-LEVEL SECURITY CONTROL WHICH WILL ALLOW THE COMPUTER TO PROCESS SEVERAL LEVELS OF CLASSIFIED MATERIALS WHILE PROVIDING COMPUTER ACCESS TO INDIVIDUALS WITH DIFFERING LEVELS OF SECURITY CLEARANCE. SINCE NO SUCH CONTROL CURRENTLY EXISTS, MILITARY COMPUTERS CAN ONLY PROCESS ONE LEVEL OF CLASSIFIED MATERIAL AT A TIME. PENETRATION EXERCISES HAVE SHOWN THE INTERNAL CONTROLS OF CURRENT COMPUTERS TO BE VULNERABLE. DEVELOPMENT OF AN EFFECTIVE REFERENCE MONITOR SYSTEM MUST INCLUDE TWO BASIC FUNCTIONS OF DETERMINING WHETHER TO ALLOW A USER ACCESS TO COMPUTER DATA AND MONITORING USE OF THE DATA ONCE ACCESS IS GRANTED. WITHOUT SOME FORM OF REFERENCE MONITOR, EVEN A MANUAL SYSTEM, NO SECURITY IS POSSIBLE. CHARTS, GRAPHS, AND REFERENCES ARE PROVIDED. (KCP).