1. A method for supervising the security of a computer system (SY) comprising several elementary computer items (BI), each elementary item being supervised in dependence on base measurements (MB) representative of predetermined states of the elementary item, and several gathering items (Ble, Big) respectively gathering elementary items, characterized in that the method comprises determining (DI 6 ) several security indicators (I) of different types for each supervised elementary item (BI), each security indicator being determined according to a respective function (AMD, AME, AAM, AAG) of base measurements (MB) associated with the security indicator, wherein the determining (DI 6 ) of a security indicator of a given type (I) of an elementary item (BI) further comprises as a result of a modification (DI 1 ) of one (MBm) of the base measurements associated with the security indicator (I), estimating (DI 2 ) a derived measurement (MD) according to a function (AMD) of the modified base measurement (MBm) and at least another base measurement (MB) interdependent with the modified base measurement, and estimating (DI 3 ) a metric (ME) according to a function (AME) of the estimated derived measurement (MD) and at least a second derived measurement (MD) according to a function of interdependent base measurements (MB) associated with the security indicator of a given type (I) and different previous base measurements, the security indicator of a given type (I) being determined according to a function dependent on the estimated metric (ME); and determining (DI 7 ) several security indicators (IA(BIe)) of different types for each gathering item, each security indicator of a given type of a gathering item being determined according to a respective function (AAIe) of the security indicators (I) of the given type of the elementary items (BIp) gathered in the gathering item (Ble, Big).