THE PROBLEM AT HAND IS CONTROLLING ACCESS TO DATA IN COMPUTERIZED INFORMATION SYSTEMS LINKED FOR USE BY MULTIPLE GOVERNMENT AGENCIES. THE PROPOSED SOLUTION IS BASED ON THE USE OF ONE OR MORE NETWORK SECURITY CENTERS AS GLOBAL ACCESS CONTROL AND AUDITING MECHANISMS, AND ON A 'SECURITY INTERFACE' BETWEEN EACH SITE AND THE NETWORK. THE INTERFACE INCLUDES A REMOTELY KEYABLE CRYPTOGRAPHIC DEVICE. BEFORE A COMMUNICATION CAN BE MADE BETWEEN A USER TERMINAL AND HOST COMPUTER IN THE NETWORK, THE USER MUST FIRST COMMUNICATE WITH THE SECURITY CENTER, WHICH, LIKE THE TERMINAL AND THE HOST COMPUTER, CONTAINS THE CRYPTOGRAPHIC DEVICE. THE SYSTEM CONTROLS ACCESS TO DATA CONTAINED IN THE NETWORK AND KEEPS TRACK OF ILLEGAL ACCESS ATTEMPTS. TECHNICAL DETAILS OF THE OPERATION OF THE NETWORK SECURITY CENTER ARE PROVIDED, TOGETHER WITH RECOMMENDATIONS FOR IMPLEMENTING CENTERS TO SUIT THE NEEDS OF VARIOUS NETWORKS. IT IS NOTED THAT THE SECURITY CENTER APPROACH CAN EFFECTIVELY CONTROL ACCESS, COLLECT AUDIT DATA, AND PROVIDE PROTECTION AGAINST UNAUTHORIZED MODIFICATION OF DATA BASES. IT IS FURTHER NOTED THAT, BECAUSE MULTIPLE CENTERS CAN OPERATE TOGETHER, THE PROPOSED SECURITY APPROACH CAN TAKE INTO ACCOUNT SUCH ISSUES AS MODULAR EXPANDABILITY, REGIONAL SUBNETWORKS, AND LOCAL CONTROL OVER RESOURCES. (LKM)