1. A method executed by a processor of populating a software catalogue with software product identifiers corresponding to software products being discovered on a plurality of data processing systems, the method including the steps of: scanning file systems of the plurality of data processing systems for detecting occurrences of sets of files, each of the sets being indicative of a licensed software product being installed on a corresponding data processing system; normalizing the sets of files; for each of the normalized sets, determining a corresponding product signature using a footprint associated with an installation of the licensed software product, the product signature being associated with the software product, the footprint comprising size and checksum pairs and information of an identified file and information of a second file which occur in all the sets containing the identified file; and storing the product signature and an associated software product identifier in the software catalogue, wherein the signature in the software catalogue is used to identify an invocation of the licensed software product.