Patent ID: 7398315

Claim:
In a sending computer system that is network connectable to one or more receiving computer systems, the sending computer system being configured to send electronic messages to the receiving computer systems, a method for verifying that responses to a connection initiation sent by the sending computer system originate from a designated receiving computer system, the method comprising: an act of sending connection initiation data to a designated receiving computer system, the connection initiation data including a purported sending address of the sending computer system; an act of receiving altered connection establishment data that includes address validation data and at least a portion of non-standard data that is not otherwise included in such a connection establishment, such that the inclusion of the portion of non-standard data substantially decreases the likelihood of providing an appropriate connection response without knowing that the portion of non-standard data is to be provided in the connection response; an act of verifying that the connection response was received from the designated receiving computer system based on a determination that the connection response included the address validation data and the portion of non-standard data; an act of generating an appropriate connection response based on the address validation data and the portion of non-standard data, the response including the portion of non-standard data in a form recognized by the verified receiving computer system as an appropriate form; and an act of sending the appropriate connection response data to the receiving computer system.