A programmable personal device, in particular an implantable medical device, such as a cardiac pacemaker, defibrillator or the like, comprising the components: a data communication interface, which is designed such that the personal device may receive data containing programming instructions via the data communication interface; a memory, which is designed to store at least one instruction identifier; and a programmable controller for controlling functions of the personal device on the basis of control parameters, which programmable controller is at least indirectly connected to the data communication interface and is designed at least to accept a programming instruction via the data communication interface and to extract an instruction identifier from the programming instruction and compare it to the stored instruction identifier and only to execute a programming instruction if the instruction identifier contained in a particular programming instruction corresponds to the stored instruction identifier and otherwise not to execute the particular programming instruction received, wherein the programmable controller is designed, after execution of a programming instruction, to store a new instruction identifier in the memory and/or to generate a new instruction identifier and/or to cause the transmission of a new instruction identifier via a data communication interface to an external device (20; 30; 40); wherein the programmable controller is also designed to append the instruction identifier belonging to a programming instruction last executed or to append the new instruction identifier to data that have been detected or generated by the personal device after the programming instruction last executed and that are transmitted from the programmable controller to the external device (20, 30, 40). a data communication interface, which is designed such that the personal device may receive data containing programming instructions via the data communication interface; a memory, which is designed to store at least one instruction identifier; and a programmable controller for controlling functions of the personal device on the basis of control parameters, which programmable controller is at least indirectly connected to the data communication interface and is designed at least to accept a programming instruction via the data communication interface and to extract an instruction identifier from the programming instruction and compare it to the stored instruction identifier and only to execute a programming instruction if the instruction identifier contained in a particular programming instruction corresponds to the stored instruction identifier and otherwise not to execute the particular programming instruction received, wherein the programmable controller is designed, after execution of a programming instruction, to store a new instruction identifier in the memory and/or to generate a new instruction identifier and/or to cause the transmission of a new instruction identifier via a data communication interface to an external device (20; 30; 40); wherein the programmable controller is also designed to append the instruction identifier belonging to a programming instruction last executed or to append the new instruction identifier to data that have been detected or generated by the personal device after the programming instruction last executed and that are transmitted from the programmable controller to the external device (20, 30, 40).