Abstract: The invention relates to the field of providing security to vehicles, specifically to a system and a method for detecting the connection of unauthorized devices. A system for detecting unauthorized connected devices in a vehicle comprises at least one electronic device of the vehicle, which is connected via an electrical bus to a module for detecting unauthorized devices consisting of a measurement unit, an analog-digital converter, a digital signal processing unit, a buffer unit and a comparator unit. A method for detecting unauthorized devices includes measuring the parameters of an electrical signal at a first moment and a second moment in time, with subsequent formation of an electrical signal spectrum. The electrical signal spectrum at the first moment in time is set as a threshold, on the basis of which a comparison is made with that received in the second time period. The accuracy of detecting unauthorized connected devices is increased.