Abstract: A method to mask static cell identifiers or static location area codes of a mobile network a mobile terminal and a masking module integrated in equipment belonging to the architecture of the network under consideration, of generating all or part of dynamic cell identifiers or dynamic location area codes from static identifiers or codes so as to make their geographical conversion impossible for an outside service other than services authenticated by the operator. The disclosed embodiments propose a masking device to mask static identifiers or codes including either a module masking static identifiers or codes, integrated in a BSC for GPS or GPRS or in a RNC for UMTS, or another masking module masking all or part of the static identifiers or codes integrated in network equipment close to the operator's platform.