We only speak about the CAN bus to take an example, because the different attacks on bus like FlewRay, ByteFlight, Most and Lin use retro engineering and the main argument to improve their security is to encrypt data packets. We just describe them a bit:

  • CAN: Controller Area Network, developed in the early 1980s, is an event-triggered controller network for serial communication with data rates up to one MBit/s. CAN messages are classified over their respective identifier. CAN controller broadcast their messages to all connected nodes and all receiving nodes decide independently if they process the message.
  • FlewRay: Is a deterministic and error-tolerant high-speed bus. With a data rate up to 10 MBit/s.
  • ByteFlight: Is used for safety-critical applications in motor vehicles like air-bags. Byteflight runs at 10Mbps over 2 or 3 wires plastic optical fibers.
  • Most: Media Oriented System Transport, is used for transmitting audio, video, voice, and control data via fiber optic cables. The speed is, for the synchronous way, up to 24 MBit/s and asynchronous way up to 14 MBit/s. MOST messages include always a clear sender and receiver address.
  • LIN: Local Interconnect Network, is a single-wire subnet work for low-cost, serial communication between smart sensors and actuators with typical data rates up to 20 kBit/s. It is intended to be used from the year 2001 on everywhere in a car, where the bandwidth and versatility of a CAN network is not required.

On just about every vehicle, ECUs (Electronic Control Units) communicate over a CAN bus, which is a two-wire bus using hardware arbitration for messages sent on the shared medium. This is essentially a trusted network where all traffic is visible to all controllers and any controller can send any message.

A malicious ECU on the CAN bus can easily inject messages destined for any other device, including things like the instrument cluster and the head unit. There are common ways for hardware to do USB to CAN and open source software to send and receive messages. For example, there is a driver included in the Linux kernel that can be used to send/receive CAN signals. A malicious device on the CAN bus can cause a great number of harmful things to happen to the system, including: sending bogus information to other devices, sending unintended commands to ECUs, causing DOS (Denial Of Service) on the CAN bus, etc.

Domain Tech name Recommendations
Connectivity-BusAndConnector-Bus-1 CAN Implement hardware solution in order to prohibit sending unwanted signals.

See Security in Automotive Bus Systems for more information.


For the connectors, we supposed that they were disabled by default. For example, the USB must be disabled to avoid attacks like BadUSB. If not, configure the Kernel to only enable the minimum require USB devices. The connectors used to diagnose the car like OBD-II must be disabled outside garages.

Domain Tech name Recommendations
Connectivity-BusAndConnector-Connectors-1 USB Must be disabled. If not, only enable the minimum require USB devices.
Connectivity-BusAndConnector-Connectors-2 USB Confidential data exchanged with the ECU over USB must be secure.
Connectivity-BusAndConnector-Connectors-3 USB USB Boot on a ECU must be disable.
Connectivity-BusAndConnector-Connectors-4 OBD-II Must be disabled outside garages.