<p>Online disinformation campaigns are different from other attempts at deception that have existed for millennia, and they require new and more effective mechanisms to counteract them. Modern disinformation campaigns use individuals’ private personal information to craft stories carefully designed to manipulate specific readers. They again use this information to direct those stories to those readers who will be most sympathetic and away from readers who will detect the attempted manipulation and experience backlash. These campaigns undermine individual agency and human dignity and polarize societies, destroying societal cohesion, which is why disinformation campaigns have been called an existential threat to human civilization. Limiting the harm of disinformation is complicated by the need to preserve freedom of speech and avoid the appearance of bias, as well as by the resistance of social media platforms that find disinformation campaigns profitable. We use simulation modeling to explore the effectiveness of mechanisms to limit the spread of disinformation and offer guidance to regulators.</p>