Controller Area Network

(also CAN bus)

Controller Area Network definition

A Controller Area Network is a vehicle bus communication protocol that facilitates communication among various in-vehicle systems without a host computer. Bosh designed it in the 1980s as a part of automotive electronics for the interconnection of electronic control units (ECUs) in vehicles. Since then, it has also been used in other contexts, including industrial automation and medical equipment.

The CAN protocol has helped advance automotive and industrial networking systems, enable efficient communication between ECUs, and develop advanced features and diagnostics in modern vehicles and equipment.

See also: replay attack

Vulnerabilities associated with CAN bus

Lack of authentication and encryption

CAN does not support secure authentication or encryption. Any controller on the network can send a message that looks legitimate to any other controller.
Attackers can inject malicious messages into the network or eavesdrop on the communication between ECUs.

Denial-of-service (DoS) attacks

By flooding the CAN bus with high-priority messages, an attacker can perform a DoS attack, preventing other ECUs from communicating effectively.

Error flag and bus-off attacks

If CAN detects an error in a message, it sends an error flag, and if it encounters too many errors, it goes into a “bus off” state and stops communicating.
Attackers can exploit this by deliberately inducing errors in messages from specific nodes, causing them to enter the “bus off” state and effectively silencing them.

Replay attacks

An attacker can capture and record legitimate CAN messages and later replay them to induce unintended behavior from the vehicle systems.
For example, a replayed message that originally commanded the windows to roll down could be used at an inappropriate time.