Phenomenons like Social Networks, Cloud Computing or Internet of Thing are unknowingly generating unimaginable quantities of data. In this context, Open Source Intelligence (OSINT) exploits such information to extract knowledge that is not easily appreciable beforehand by the human eye. Apart from the political, economic or social applications OSINT may bring, there are also serious global concerns that could be covered by this paradigm such as cyber crime and cyber threats. The paper at hand presents the current state of OSINT, the opportunities and limitations it poses, and the challenges to be faced in the future. Furthermore, we particularly study Spain as a potential beneficiary of this powerful methodology.