The break of the citizens' confidence in the information conveyed to them by the media is not a minor issue. In a regime of opinion and in a globalized society in which the issues that directly affect us are beyond our reach or understanding, the mediation work of journalists is essential. For this reason, the phenomenon of fake news in the so-called post-truth era is of paramount importance because it undermines the notion of truth, which is supposed to be the heart and raison d'être of the journalistic profession. The task of journalists is to provide public opinion with true or honestly truthful information that allows citizens to form a complete idea of what is happening and, based on this, make well-founded decisions on matters under public discussion. Without a minimum consensus on the facts, citizens are exposed to the effects of pure propaganda, their ability to decide is manipulated and the core of democracy damaged. The actions of tobacco companies to deny the lethality of tobacco, the denial of climate change, the orchestrated campaigns against the efficacy of vaccines or the unbridled dissemination of "alternative facts" in politics, have highlighted the fragility of the truth in the face of to the distorting power of unscrupulous media and irrepressible social networks.