1. A method of authenticating a user in a secure computer system comprising the steps of: transmitting from a client computer of a user to the computer system a request for a sign-on page; transmitting from the computer system to the client computer a prompt for a first user identifier; in response to said prompt, transmitting from the client computer to the computer system a request including the first user identifier, a second user identifier stored in an object stored at the client computer and a plurality of request header attributes; authenticating at the computer system the first user identifier; authenticating at the computer system the second user identifier; comparing the transmitted plurality of request header attributes with a plurality of request header attributes stored at the computer system and associated with the first user identifier; and if the first and second user identifiers are authenticated, and if the transmitted request header attributes correspond to the stored request header attributes, transmitting a success message to the client computer to be viewed by the user.