Although software products are immaterial goods, their use can bring about significant materials and energy flows. Software characteristics determine which hardware capacities are made available and how much electric energy is used by end-user devices, networks, and data centers. The connection between software characteristics and the demand for natural resources caused by the manufacture and use of ICT systems has been the object of little scientific study to date. The present study breaks new ground by exploring the effects of software on the indirect use of natural resources by hardware. The study identifies starting points in the realm of software that can contribute to conserving natural resources or at least to slowing further growth of their use by ICT systems. A particular focus of the study is on methodological problems arising when assessing the resource use of software products. Such problems include difficulties in defining functional units as well as problems of measurement and allocation. Approaches such as standardizing patterns of use and benchmarks as well as defining and implementing sustainability requirements in the software development process are sketched out as possible solutions. Based on these considerations, the study formulates initial recommendations for action in the areas of research and standardization, product labeling, information for users concerning configuration, best practice guides as well as training and professional development.