The Four Horsemen of the Infocalypse is a term for internet criminals, or the imagery of internet criminals.
A play on Four Horsemen of the Apocalypse, it refers to types of criminals who use the internet to facilitate crime and consequently jeopardize the rights of honest internet users. There does not appear to be an exact definition for who the Horsemen are, but they are usually described as terrorists, drug dealers, pedophiles, and organized crime. Other sources use slightly different descriptions but generally refer to the same types of criminals. The term was coined by Timothy C. May in 1988, who referred to them as "child pornographers, terrorists, drug dealers, etc." when discussing the reasons for limited civilian use of cryptography tools. Among the most famous of these is in the Cypherpunk FAQ