A method and a corresponding apparatus for metering usage of software products on a computer are proposed. The metering system is based on the use of a software catalogue. The software catalogue lists all the known products to be metered; each product is identified by one or more executable modules indicative of its running. A licensing agent detects the executable modules that have been launched. For each executable module, the system checks if a corresponding product is listed in the catalogue, and can decide an appropriate action, or simply meter the usage of the product for future reporting and invoicing activity. If no corresponding product is found in the catalogue, the method according to the present invention performs a similarity check between the unknown detected module and the product identifiers existing on the catalogue. Sometimes the difference between a new product and a catalogued one is very limited. If such difference is evaluated to be within a predetermined threshold, than the unknown module is added to the catalogue.