A method of detecting manipulation of data on a Controller Area Network (CAN) bus, and a device performing the method. In an aspect, the method includes detecting manipulation of data on a CAN bus to which the device is connected. The method comprises detecting that bus impedance is below a threshold bus impedance value, detecting whether or not CAN node arbitration currently may occur on the CAN bus upon detecting that the bus impedance is below the threshold bus impedance value, and if not determining that an attempt to manipulate data on the CAN bus has occurred.