A method for loading, installing and running software, called loading units, having different levels of confidence by a data processing unit (1). The method includes at least associating at least one structure of information data concerning security requirements and characteristics of this loading unit with each loading unit (2, 3, 7); associating a dynamic data structure (10) representative of the state of security in the data processing unit (1) to the data processing unit (1); validating the security requirements and characteristics of each loading unit (2, 3, 7) with regard to the state in the data processing unit (1) contained in the dynamic data structure (10via an autonomous security module (9), and; if the validation is positive, authorizing, via the security module (9), the loading, installation or running of the loading unit (2, 3, 7).