US Patent 8151107 Method and system for detecting concurrent logins

Concurrent login detection system includes: a message receiving unit configured for receiving a log message which is indicative of a user identifier of a user, login/logout state of the user, and a session identifier, from an external server; a corresponding message retrieval unit configured for retrieving a corresponding message of the received log message from a memory wherein the corresponding message is a log message containing the same user identifier and the same session identifier with those contained in said received log message; and a message processor configured for removing said received log message and said retrieved corresponding message from the memory if the corresponding message is retrieved from the message buffer, and for storing said received log message in the memory if said corresponding message is not retrieved from the memory.