Described systems and methods enable a swift and efficient detection of fraudulent Internet domains, i.e., domains used to host or distribute fraudulent electronic documents such as fraudulent webpages and electronic messages. Some embodiments use a reverse IP analysis to select a set of fraud candidates from among a set of domains hosted at the same IP address as a known fraudulent domain. The candidate set is further filtered according to domain registration data. Online content hosted at each filtered candidate domain is further analyzed to identify truly fraudulent domains. A security module may then prevent users from accessing a content of such domains.