Abstract: An input device lock and method for preventing unauthorized access to the computer. The device is a lock switch that selectively enables or disables the line that effectuating data flow between the input device and the computer. Any input device may be selectively disabled using the present invention including a keyboard, mouse, track ball, joy stick, light pen, or other hand-held controller for example. Depending on the computer's configuration, the data flow-effectuating line is known as the data line, input/output line, signal line, or clock line. When the flow-effectuating line is disabled by this device, no data is transmitted from the input device to the computer and therefore access to the computer is controlled. No other wires inside the cable are affected; in particular, the power and ground lines are not broken. The lock switch is the style that allows the key to be inserted or removed only when the lock switch is in the input device disabled state.