Abstract: A timer operated hardware switching device to control the connection between a computer and telephone or data circuit. The device improves the security of the computer by limiting external access from the Internet or other networks. Security software programs such as fire walls are enhanced by the invention, which prevents electronic attacks during periods when the switching device is in the disconnected state. The device is simple to understand and can be easily verified in operation. Additionally, such a device can be used with conventional telephone applications to prevent calls from being made during specific time periods. The invention can be embodied as a standalone device, a device for use with a conventional power timer, and a device built into a computer or other computer accessory.