  The innovations of vehicle connectivity have been increasing dramatically to
enhance the safety and user experience of driving, while the rising numbers of
interfaces to the external world also bring security threats to vehicles. Many
security countermeasures have been proposed and discussed to protect the
systems and services against attacks. To provide an overview of the current
states in this research field, we conducted a systematic mapping study on the
topic area "security countermeasures of in-vehicle communication systems". 279
papers are identified based on the defined study identification strategy and
criteria. We discussed four research questions related to the security
countermeasures, validation methods, publication patterns, and research trends
and gaps based on the extracted and classified data. Finally, we evaluated the
validity threats, the study identification results, and the whole mapping
process. We found that the studies in this topic area are increasing rapidly in
recent years. However, there are still gaps in various subtopics like
automotive Ethernet security, anomaly reaction, and so on. This study reviews
the target field not only related to research findings but also research
activities, which can help identify research gaps at a high level and inspire
new ideas for future work.
