Computer Implemented Method and System for Protecting a Patient Critical Firmware Function of an Implantable Medical Device

System for protecting a patient critical firmware function of an implantable medical device, in particular a pacemaker, a defibrillator and/or a neuro-stimulator, against unintended execution, the system comprising:

• an implantable medical device and a programmer, wherein the implantable medical device is configured to receive a request by the programmer for execution of a patient critical firmware function of the implantable medical device, wherein the implantable medical device is configured to verify that a user associated with the request is authorized to run the patient critical firmware function, wherein the implantable medical device is configured to read a first checksum from a first memory area of the implantable medical device or to provide a first checksum as part of a code area of the patient critical firmware function of the implantable medical device, wherein the first checksum does not match a correct checksum associated with the patient critical firmware function of the implantable medical device, wherein the implantable medical device is configured to read a second checksum from a second memory area of the implantable medical device, wherein the second checksum matches the correct checksum associated with the patient critical firmware function of the implantable medical device, wherein the implantable medical device is configured to write the second checksum to a third memory area of the implantable medical device from which a checksum is read before execution of the patient critical firmware function of the implantable medical device, wherein the implantable medical device is configured to compute the correct checksum associated with the patient critical firmware function of the implantable medical device and to compare it to the second checksum, and wherein the implantable medical device is configured to execute the patient critical firmware function of the implantable medical device if the second checksum and the correct checksum match.