## 5 Remote Monitoring Technologies
This is achieved by detecting the unique set of RF waveform features pertaining to a transmitter, so called fingerprint, and the timing of each transmission [125]. These can then be used to associate each message with a unique transmitter, thus providing an indication of the location and type of each sensor that is communicating with this transmitter. To counteract this fingerprint and timing based snooping attack, several approaches have been proposed, e.g., signal attenuation outside of the patient's home to increase the packet loss ration of the invader; periodically transmitting signals even if they do not contain patient-related data; arbitrarily delaying messages to obscure the time at which the patient-related data is being transmitted; making the transmitted fingerprint less discoverable; sending false messages that imitate real events [117]. The open and dynamic nature of the wireless body area network and distributed patient-related data storage often results in data being accidently lost, and therefore not readily available for retrieval by clinical staff [116,123]. It has been suggested that the reliability of the wireless sensor network can be improved by employing compressed sensing theory [126]. Compressed sensing is believed to have the capacity to enhance processing capability, storage capacity, and time of testing of wireless sensing networks [127]. It is based on the premise that sparse signals as those observed in wireless sensor networks can be accurately reconstructed from a small fraction of random linear measurements. While remote monitoring technologies have been progressing steadily, remotely controlled treatment delivery and reprogramming of indwelling electronic modules is hindered by the regulatory issues, with law restrictions currently prohibiting remote reprogramming outside of the clinic [5,124]. [PERSON] and [PERSON] suggested a number of potential security and privacy risks associated with the remote reprogramming function embedded into cochlear implants [128]. A typical cochlear device consists of a microphone worn behind the ear, an external speech processor, an indwelling signal receiver/stimulator, and a remote control unit which allows the user to change some of the settings of the implant [129]. Given the individual needs of each patient, the device is fine-tuned upon implantation to ensure the appropriate performance [130]. Clearly necessary, the remote reprogramming function also makes these devices potentially vulnerable to malicious interventions that can range from turning off the implant to render the user deaf, to reprogramming the intensity of cochlea stimulation where patient can hear sounds in the absence of corresponding external sound or suffer from a painful perception of acoustic signals [128]. A less obvious intervention, the sound processing unit can be reprogrammed to disregard the input from the microphone, replacing the external sound with the sound generated by the intruder. Such message replacement invasion may be particularly successful where the cochlear implant patient cannot receive visual confirmation of the message. Malicious modifications of implanted cardiac devices may be even more devastating to the health status of the patient, with potentially lethal outcomes [131]. This can be accomplished by giving an implanted cardiac device a command to stop operating when a patient has a cardiac episode or to induce an episode by triggering defibrillation [132]. A battery-powered implantable cardioverter defibrillator can also be saturated with external communication requests from the unauthorized device, thus posing a risk of denial-of-service attack and potentially dangerously depleting the battery power level of the device. Information extraction and invasion of privacy have also been identified as a potential security issue [129].