The carwhisperer project intends to sensibilise manufacturers of carkits and other Bluetooth appliances without display and keyboard for the possible security threat evolving from the use of standard passkeys. A Bluetooth passkey is used within the pairing process that takes place, when two Bluetooth enabled devices connect for the first time. Besides other public data, the passkey is a secret parameter used in the process that generates and exchanges the so-called link key. In Bluetooth communication scenarios the link key is used for authentication and encryption of the information that is exchanged between the counterparts of the communication. The cw_scanner script is repeatedly performing a device inquiry for visible Bluetooth devices of which the class matches the one of Bluetooth Headsets and Hands-Free Units. Once a visible Bluetooth device with the appropriate device class is found, the cw_scanner script executes the carwhisperer binary that connects to the found device (on RFCOMM channel 1) and opens a control connection and connects the SCO links. The carwhiperer binary connects to the device found by the cw_scanner. The passkey that is required for the initial connection to the device is provided by the cw_pin.pl script that replaces the official Bluez PIN helper (graphical application that usually prompts for the passkey). The cw_pin.pl script provides the passkey depending on the Bluetooth address that requests it. Depending on the first three bytes of the address, which references the manufacturer, different passkeys are returned by the cw_pin.sh script. In quite a few cases the preset standard passkey on headsets and handsfree units is '0000' or '1234'. Once the connection has been successfully established, the carwhisperer binary starts sending audio to, and recording audio from the headset. This allows attackers to inject audio data into the car. This could be fake traffic announcements or nice words. Attackers are also able to eavesdrop conversations among people sitting in the car. Ideally, the carwhisperer is used with a toooned dongle and a directional antenna that enhances the range of a Bluetooth radio quite a bit. (see Long-Distance-Snarf experiment)