The Digital Munition group have found a vulnerability that allows unauthorized remote access to PC Bluetooth audio profile.
According to the text of the advisory, users with proper software can eavesdrop a PC that has Widcomm Bluetooth software and a microphone, or play audio on the target PC.
This happens because the default security settings for headset services is low, not requiring any authentication. Of course this requires close range to work.
The exploit can be only accomplished if the victim's PC is running the Widcomm Bluetooth software. It won't affect other stacks such as the Microsoft Bluetooth (Service Pack 2) or BlueSoleil.
A workaround this vulnerability is to set authentication for the Headset Audio Gateway profile, and set Bluetooth to non-discoverable mode.
Accordin to F-Secure, setting your PC Bluetooth to non-discoverable will not remove the problem completely, as your PC can still be found by brute force scanning. But it will significantly limit the exposure.