The invention relates to a portable data carrier system having a control unit, a body, a data memory integrated in a chip, in which security-relevant data can be stored, and a feature for permitting information exchange between the control unit and an external access unit. A security device of the chip transmits a security signal that is influenced by an influencing feature integrated in the body and non-electrically connected with the security device. A detection feature of the security device detects the influenced security signal, an evaluation feature evaluates the detected, influenced security signal, and a blocking feature blocks a security-critical operating state of the data carrier system if the evaluation feature does not recognize a security signal influenced in the expected way.