Multi-level security network system

A method for operating a multi-level secure network having a plurality of host computers accessible to users through input of a single user identifier and a network security controller, each of which are connected to a network medium that has access to an untrusted line, the method comprising:

• generating at the network security controller a plurality of user profiles for each user identifier inputted by a user, each of said user profiles defining at least one of multiple destinations which the user is authorized to access through discretionary access control and mandatory access control security mechanisms, to define virtual private networks of communication comprising subsets of host computers;
• authorizing a user identifier that a user inputs at a host computer;
• permitting, at the host computer, the authorized user to select one of said plurality of user profiles associated with the user identifier;
• sending one of said plurality of user profiles from said network security controller, as selected by the authorized user, to said host computer;
• and
• restricting access of the host computer to the destinations defined in the selected user's profile.

A method for controlling a sending computer to transmit information to a receiving computer over a computer network, the method comprising:

• providing a security system at each sending computer and receiving computer;
• setting user identification information at each security system for enabling a user to access the computer associated with the security system;
• setting a plurality of user profiles at one or more of the security systems to enable a user, based on a user's user identifier, to select one of said plurality of user profiles, each user profile defining one or more destinations that the user is authorized to communicate with;
• providing a network security controller on said computer network for receiving from said security system the identification of an authorized user identifier and the selected user profile and for forwarding the selected user profile to the security system for said authorized user identifier, including providing discretionary access control and mandatory access control policies for each user profile;
• receiving information to be transmitted from the sending computer to the receiving computer at the sending computer security system;
• implementing security mechanisms at a network layer of ISO protocol hierarchy to determine whether communication is authorized from the sending computer to the receiving computer by determining if the receiving computer is in a transmit list and consistent with a transmit security window through discretionary access control and mandatory access control, respectively and, if either condition is not satisfied then terminating the transmission of information and sending termination notice to the network security controller, otherwise encrypting the information to be transmitted;
• and
• transmitting the encrypted information to the security system of the receiving computer over the computer network.