Zeus is a Trojan horse designed to steal personal financial data such as passwords and bank details. It was first discovered in 2007 and roped infected devices into a botnet, a large network of computers controlled by hackers. Cybercriminals used the botnet to steal money from major corporations and banks. The documented financial damage from the Zeus Trojan was estimated to be around $70 million, but experts believe that costs associated with recovery could be significantly higher.