Münchausen by Internet is a pattern of behavior in which Internet users seek attention by feigning illnesses in online venues such as chat rooms, message boards, and Internet Relay Chat (IRC). It has been described in medical literature as a manifestation of factitious disorder or factitious disorder by proxy. Reports of users who deceive Internet forum participants by portraying themselves as gravely ill or as victims of violence first appeared in the 1990s due to the relative newness of Internet communications. The pattern was identified in 1998 by psychiatrist Marc Feldman, who created the term "Münchausen by Internet" in 2000. It is not included in the fourth revision of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR).
The development of factitious disorders in online venues is made easier by the availability of medical literature on the Internet, the anonymous and malleable nature of online identities, and the existence of communication forums established for the sole purpose of giving support to members facing significant health or psychological problems. Several high-profile cases have demonstrated behavior patterns which are common among those who pose as gravely ill, victims of violence, or whose deaths are announced to online forums. The virtual communities that were created to give support, as well as general non-medical communities, often express genuine sympathy and grief for the purported victims. When fabrications are suspected or confirmed, the ensuing discussion can create schisms in online communities, destroying some and altering the trusting nature of individual members in others.