Another avatar-based system is one wherein an image is automatically generated based on the identity of the poster. Identicons are formed as visually distinct geometric images derived from a digest hash of the poster's IP address. In this way, a particular anonymous user can be uniquely identified from session to session without the need for registration or authentication. In the cases where registration has occurred, the identicon serves as a means to associate a particular user with a particular geometric representation. If an account is compromised, a dissimilar identicon will be formed as the attacker is posting from an unfamiliar IP address.