Several embodiments of computer security systems are described and which are adapted to grant an authorized individual access to a secured domain, such as a computer or data stream. In one embodiment, the security system comprises: an analyzing means for receiving first and second passwords, each of said passwords being transmitted over a first communication channel, analyzing said first password, transmitting a first signal output only if said first password is authorized, and granting access to said secured domain only if said second password is substantially identical to a code; and a random code generating means for generating said code, transmitting said code over a second communication channel upon receipt of first signal output, and transmitting said code to said analyzing means; and a notification means for receiving said code and for notifying said authorized individual of the identity of said code.