This security system reads a code generated by turning the key (as I understand it) and the only security feature is disabling the starter when the wrong code is read.
What I can't remember is how a different code is generated by each turn of the key.
When you turn the key it tells the BCM what code to expect from the next turn of the key.
Some systems use a transmitter in the key and a reciever antenna ring around the ignition switch (BMW and FORD) But GM's is slightly different
In any case the system is passive with no input from the driver to arm,it does not sound a horn,blink lights,just disables the starter.