Abstract: A method consists in assigning an authorization level (AUTH) to a client object and a "dynamic" sensitivity level (DSL) to a method (or data processing procedure) of a server object (ProcObjSv). The dynamic sensitivity level is computed based on static sensitivity levels (SSLs) at the moment when the server object is instantiated. The authorization level of the client object is passed to the method of the server object when the method of the server object is invoked by the client object, and this authorization level (AUTH) is compared with the dynamic sensitivity level (DSL) of the method in order to control access. The method makes it possible to implement a multi-level security model.

Abstract: A facility for detecting intrusions and suspect users in a computer installation, and a security system incorporating such a facility that makes use of surveillance data relating to the operation of the installation. The facility includes elements for modelling the computer installation, its users, and their respective behavior with the help of a semantic network; elements for comparing the modellized behavior of the system and of its users relative to modellized normal behavior; elements for interpreting observed anomalies in terms of intrusions and of intrusion hypothesis; elements for interpreting observed intrusion hypotheses and intrusions in order to indicate them and enable restraint actions to be prepared. Elements are provided to evaluate the degree of suspicion of users. The elements co-operate with one another for the purpose of providing information.