A FUDster is a person who spreads FUD, short for fear, uncertainty and doubt, about a cryptocurrency, a project or the market as a whole. The label is used on social media and in crypto forums for people who post negative claims, warnings or rumours, sometimes to drive prices down so they can buy cheaply or profit from short selling. It is also thrown, often unfairly, at journalists, regulators and analysts who raise genuine concerns, which lets holders dismiss criticism without answering it. The FUDster is the opposite of the shill, who hypes a coin to push its price up; see shill or shilling. Deliberately spreading false information to move prices can amount to market manipulation in many jurisdictions.