Information
When Bluetooth is set to discoverable mode, the Mac sends a signal indicating that it's available to pair with another Bluetooth device. When a device is 'discoverable' it broadcasts information about itself and its location. Starting with OS X 10.9 Discoverable mode is enabled while the Bluetooth System Preference is open and turned off once closed. Systems that have the Bluetooth System Preference open at the time of audit will show as Discoverable.
Rationale:
When in the discoverable state an unauthorized user could gain access to the system by pairing it with a remote device.
Solution
Perform the following to implement the prescribed state:
Starting with OS X (10.9) Bluetooth is only set to Discoverable when the Bluetooth System Preference is selected. To ensure that the computer is not Discoverable do not leave that preference open.