# CAN bus **slug:** `can-bus` · **URL:** `/knowledge/glossary/can-bus/` · **category:** Automotive · **reviewer:** Tatiana K. ### Definition CAN bus (Controller Area Network) is a serial communication protocol designed for in-vehicle Electronic Control Unit (ECU) communication. It allows multiple ECUs — engine, transmission, brakes, infotainment — to exchange messages on a shared two-wire bus without a central host. ### What it means Developed by Bosch in 1986 and standardized as ISO 11898, CAN bus is the dominant in-vehicle network protocol in passenger vehicles. CAN-FD (Flexible Data-rate) extends the original specification with higher bandwidth (up to 8 Mbit/s) and larger payloads (up to 64 bytes per frame). Messages broadcast on the bus with priority-based arbitration; any ECU can read any message. The lack of authentication or encryption in the base CAN specification creates the primary security concern. An attacker with physical access to the bus — through the OBD-II port, a compromised telematics gateway, or a connected infotainment system — can inject arbitrary messages, replay captured frames, or perform denial-of-service via bus saturation. Modern vehicles increasingly use CAN gateways with message filtering or full security extensions (CAN-FD with Secure Onboard Communication / AUTOSAR SecOC) to constrain cross-zone message injection. For offensive-security assessment, CAN bus testing typically includes: passive bus capture and dictionary attacks against unknown PIDs (parameter IDs), active replay of captured frames in a controlled lab environment, fuzzing of high-rate messages, and gateway-bypass attempts. The [TARA Quality Anti-Patterns](/research/tara-quality-patterns/) note discusses related methodology issues we see in automotive engagement portfolios. ### Where it appears at Melina Central to engagements under [Automotive Security](/services/automotive-security/). CAN bus testing is one of the standard scope items in an in-vehicle network assessment. ### Related terms - [OBD-II](/knowledge/glossary/obd-ii/) - [ECU](/knowledge/glossary/ecu/) - [TARA](/knowledge/glossary/tara/) - [ISO/SAE 21434](/knowledge/glossary/iso-sae-21434/) - [DoIP](/knowledge/glossary/doip/) (P1.5) ### Authoritative sources - [ISO 11898-1:2024](https://www.iso.org/standard/86384.html) — Road vehicles — Controller area network (CAN) — Part 1: Data link layer and physical signalling - [Bosch CAN Specification 2.0](https://www.bosch-semiconductors.com/media/ip_modules/pdf_2/can_fd_spec.pdf) - [AUTOSAR SecOC specification](https://www.autosar.org/fileadmin/standards/R23-11/CP/AUTOSAR_SWS_SecureOnboardCommunication.pdf) ---