In March 2018, the U.S. DHS and the FBI issued a joint critical alert (TA18-074A) of an ongoing campaign by Russian threat actors targeting U.S. government entities and critical infrastructure sectors. The campaign targets critical infrastructure organizations mainly in the energy sector and uses, among other techniques, Open Source Intelligence (OSINT) to extract information. In an effort to understand the extent and quality of information that can be collected with OSINT, we shadow the threat actors and explore publicly available resources that can generate intelligence pertinent to power systems worldwide. We undertake a case study of a real, large-scale power system, where we leverage OSINT resources to construct the power system model, validate it, and finally process it for identifying its critical locations. Our goal is to demonstrate the feasibility of conducting elaborate studies leveraging public resources, and inform power system stakeholders in assessing the risks of releasing critical information to the public.