| CPC G06F 21/55 (2013.01) [G06F 21/602 (2013.01)] | 18 Claims |

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1. An intrusion detection system which performs detection on unauthorized data which enters into a control device of a motor vehicle where the control device is connected by way of a communications line, the intrusion detection system, comprising:
a monitor listing for setting a rule on which determination is performed whether communications data is normal or abnormal in every one of respective states;
intrusion detection circuitry for acquiring communications data flowing through the communications line, and for performing, by comparing said communications data with said monitor listing, determination on a presence or absence of abnormality in said communications data;
state management circuitry for acquiring a state of a host motor vehicle and/or that of the control device, and for changing over said monitor listing for use in the intrusion detection circuitry;
processing time management circuitry for giving rise to increasing a processing time of the intrusion detection circuitry in accordance with processing content of the intrusion detection circuitry.
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