Automotive computers, or Electronic Control Units (ECU), were originally introduced to help with fuel efficiency and emissions problems of the 1970s but evolved into integral parts of in-car entertainment, safety controls, and enhanced automotive functionality. This presentation will examine some controls in two modern automobiles from a security researcherís point of view. We will first cover the requisite tools and software needed to analyze a Controller Area Network (CAN) bus. Secondly, we will demo software to show how data can be read and written to the CAN bus. Then we will show how certain proprietary messages can be replayed by a device hooked up to an ODB-II connection to perform critical car functionality, such as braking and steering. Finally, weíll discuss aspects of reading and modifying the firmware of ECUs installed in todayís modern automobile.