Method and apparatus for ensuring secure access to a computer system (1000). The method can begin with the step of receiving in the computer system a request from an entity (using 1002). The entity can have a predetermined access authorization level for access to a first base node (110) representing an information type (102) or a computer system function (104). The system determines if the access request completes a prohibited temporal access pattern for the entity. The system also compares a minimum access level established for the first base node to the predetermined access authorization level assigned to the entity. Thereafter, the system can grant the access request only if the minimum access level for the first base node does not exceed to the predetermined access authorization level.