A method and a system for enabling secure authentication of a user in a computerized card access transaction. A card, identified by an identification number is issued to the user, containing software for generating a surrogate number referred to as a Cybercoupon for use in place of the regular card number. Online intrusion is avoided and the system is rendered portable for use on any computer equipped with a compatible operating system, by avoiding storage of any part of the system on the user's computer, placing the entire system instead on the card itself. The card contains advertising which appears on the user's computer screen. The card is protected by a password. If an incorrect password is entered more than a preset number of times, an "alert" Cybercoupon is generated containing a code advising the card issuer that an irregular attempt has been made to access the card.