In this paper, we systematically review and categorize different hardware-based firmware extraction techniques, using 24 examples of real, wide-spread products, e.g. smart voice assistants (in particular Amazon Echo devices), alarm and access control systems, as well as home automation devices. We show that in over 45% of the cases, an exposed UART interface is sufficient to obtain a firmware dump, while in other cases, more complicated, yet still low-cost methods (e.g. JTAG or eMMC readout) are needed. In this regard, we perform an in-depth investigation of the security concept of the Amazon Echo Plus, which contains significant protection methods against hardware-level attacks. Based on the results of our study, we give recommendations for countermeasures to mitigate the respective methods.
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