This work aims at describing the use of disinformation throughout technology in contexts of emergencies. After a short introduction in which the notions of emergency and disinformation are explained, the chapter analyzes the use of disinformation in two recent emergencies: international terrorism and the Covid-19 pandemic. While in the first case, disinformation took the forms of viral vigilantism or was a strategy for radicalization, during the Covid-19 pandemic disinformation was spread by public authorities or by citizens. Against this background, the article addresses, from a comparative viewpoint, the legal measures enacted in different countries to respond and limit the spread of disinformation during these two emergencies. From this analysis, the Authors draw significant practical and theoretical consequences regarding the relationship between security, technology and emergencies in the concluding remarks.