A multi-level security apparatus and method for a network employs a secure network interface unit (SNIU) coupled between each host or user computer unit and a network, and a security management (SM) architecture, including a security manager (SM) coupled to the network, for controlling the operation...http://www.google.de/patents/US5940591?utm_source=gb-gplus-sharePatent US5940591 - Apparatus and method for providing network security
