## 7 IoMT Devices and Potential Attacks  
IoMT systems can be useful for a wide range of medical conditions. In the IoMT, smart medical devices are classified into four categories based on where they are used on the human body [63]. * **Implantable Medical Devices (IMDs):** These are devices that are implanted to replace or sustain a biological structure that is absent or damaged. Furthermore, an IMD can be utilized to improve a biological structure that already exists. The primary function of such implanted devices is to monitor and transmit signals from the patient's body to other medical systems [63]. They are primarily composed of small wireless modules and health sensors that capture information such as temperature, mobility, blood glucose, and blood pressure. The pacemaker, for example, can be particularly beneficial for managing aberrant cardiac rhythms [64], and infusion pumps, such as enteral, PCA, and insulin infusion pumps, can be utilized in a range of therapies [65, 32]. Infusion pumps have been linked to a number of patient-safety issues. As a result, authentication procedures need to be developed [66]. Although a wireless connection may enhance the security risks associated with these electronic devices, it is nevertheless the most preferred communication method for their installation [11]. * **Internet of Wearable Devices (IoWDs):** These devices are worn by people to track their biometrics, which may help them improve their overall health. This category includes a variety of IoMT systems. Examples could include EEG (electroencephalography) and ECG (electrocardiography) [67, 68]. As we know, EEG can be used to monitor and record brain activities while an ECG can monitor the condition of the heart's rhythm and electrical activity. Other examples could include, for instance, smart watches that are quite popular nowadays for monitoring biometrics such as heart rate and movement; fitness trackers; activity, accelerating, and respiratory rate sensors [69, 32]; and so on. However, due to battery-life limitations and sensor accuracy, these devices are unlikely to be used to replace IMDs in critical situations [12]. * **Ambient Devices:** Although ambient devices are not used for patient treatment and monitoring, they sense the patient's environment to monitor patterns of activity and manage environmental conditions near the patient. They include [70] patient identification devices, motion detection devices, monitoring devices, implantable device chargers, and alarm devices. * **Stationary Devices:** Devices that are not generally carried by the patient are classified as stationary devices. Although such devices were previously unconnected, they may now be managed remotely to enable telemedicine treatments [71]. Examples of stationary devices include imaging devices (such as, magnetic resonance imaging (MRI), computerized tomography (CT) scanners, and X-rays) and surgical devices [72]. Low-power wireless network technologies (such as Bluetooth or Bluetooth/BLE, NFC, Zigbee, Z-Wave, and RFID) are commonly used to communicate between the body network and the personal server. Bluetooth is mostly used in wearable devices, while RFID and NFC use a short-range, low-power communication topology. Therefore, they are frequently used in implanted devices [73, 74]. On the other hand, long-range wireless technologies such as Wi-Fi, LoRa, and GSM are used by the IoMT system to provide the connection between the personal server gateway and the medical server. Different network attacks can compromise IoMT devices. This is due to a lack of standards and security controls in device production, as well as the nature of the devices and the IoMT network. Memory space, energy, and low power limits preclude them from supporting the calculation of typical cryptographic security methods. Furthermore, as the IoMT network is heterogeneous and uses multiple protocols at each layer, a single security solution will not work for all devices.