Truck fleets have a new defense against CAN bus attacks: a DIY firewall built from off-the-shelf parts. Researchers at Oak Ridge National Laboratory built ELDSentry, a microcontroller-based firewall that blocks injection of arbitrary CAN messages onto the SAE J1939 bus, the data network that links heavy-truck components.
The design targets a real weak point in modern commercial vehicles. Electronic logging devices, mandated by the Federal Motor Carrier Safety Administration since 2016, connect to the diagnostic port and almost always carry wireless interfaces. WiFi and Bluetooth Low Energy links on those ELDs give attackers a path to push forged messages onto the truck’s network, where they can interfere with vehicle control functions.
ELDSentry sits between untrusted devices and the bus, filtering traffic in real time and logging CAN data to a microSD card for forensics. The prototype uses common components: a Teensy microcontroller, CAN transceivers, and DC voltage regulators. The team’s objective is to make the hardware cheap and simple enough that fleets and owner-operators can deploy it without waiting for OEM security features.
The work was presented at the VehicleSec 2026 demo session alongside a companion J1939 simulation project. No commercial product has been announced, but the open design means shops can build and test their own units today.
