The most common way for IoT devices to connect and interact is via wireless Radio Frequency (RF) communication. There are loads of different wireless frequencies, modulations, and protocols used in today's current market. Some wireless protocols are proprietary and others are standard. Opening up a device will unveil one or multiple chips that perform wireless communication. This is definitely common for IoT gateways and hubs that are required to ingest a variety of different wireless communication protocols and frequencies. One of the advantages of wireless technology is the ability to be remote and still control a device. This is also the case when exploiting devices with wireless communication. It is important to understand the distance that each wireless technology is capable of. One wireless protocol may have a distance of 105 ft., or about 32 meters, while others can be as short as 20 cm. Amongst the many wireless protocols in the IoT ecosystem, some of the most common protocols used are Wi-Fi (802.11), ZigBee (802.15.4), Z-Wave, Bluetooth (802.15.1), and Bluetooth Low Energy.
Introduction to IoT's wireless communications
Wi-Fi
Wi-Fi has been the most common wireless technology used in many devices for years. It operates on 2.4 GHz and 5 GHz ISM bands. There are a number of Wi-Fi standards in use, such as 802.11a, 802.11b, 802.11g, 802.11n, and 802.11ac. 802.11b and 802.11g operate on the 2.4 GHz band while 802.11a, 802.11n, and 802.11ac use the 5 GHz band. There are 14 wireless channels which operate on different frequencies. Depending on the region, there are certain channels that Wi-Fi routers are allowed to broadcast on.
ZigBee
ZigBee is based on the IEEE 802.15.4 specification for the physical and media access control layers, which support low-powered wireless mesh networking. ZigBee operates on different ISM bands based on region, but mostly on 2.4 GHz worldwide with 915 MHz in the US and 868 MHz in the EU. ZigBee is comprised of a coordinator (ZC), router (ZR), and end devices (ZED). The coordinator automatically initiates the formation of the network. There is only one coordinator in a network and it's generally the trust center for authenticating and validating each device that has joined the network and has a unique network key. The router passes data from other devices and associates routes to end devices.
Routers have to be continually powered in order to properly pass messages to the network. End devices are IoT devices such as light switches, sensors, cameras, or monitors. They cannot route data inside the network but can be put to sleep in a low power mode while not transmitting. ZigBee networks are based on two security keys known as the network key and link key. The network key is used to securely transport communication and is a 128-bit key shared with all devices in the network. The link key is used to secure the unicast communication in the application layer of ZigBee. The link key is also a 128-bit key which is only shared between two devices. Link keys can be pre-installed on devices or distributed through a key exchange. Vulnerable key exchanges during device pairing is a known flaw in consumer-based ZigBee networks, which has allowed attackers to sniff the exchange network key and compromise the entire network.
A good slide deck for referencing ZigBee security flaws can be found via the ZIGBEE EXPLOITED talk given at Blackhat in 2015:
Z-Wave
Z-Wave is another low-powered wireless communication protocol that supports mesh networks with a master-slave model. It uses the sub-1 GHz band which varies by region (916 MHz in the US or 868.42 in the EU). Its physical and media access layers are ratified under ITU as the international standard G.9959. Z-Wave's range between two devices is 328 ft. or 100 meters, but it can reach up to 600 ft. or 200 meters when traffic traverses through Z-Wave products with in its mesh network. The Z-Wave network is identified by a 4 byte (32-bit) HomeID which is the controller or master node's unique ID. All nodes within the same network share the same HomeID. Each node is identified by a 1 byte (8 bits) NodeID which is provided by the controller once they are joined to the network. Nodes with different HomeIDs cannot communicate with each other. Z-Wave can use AES encryption, which is supported by Z-Wave hubs, but it is purely optional for manufacturers to implement. Z-Wave does include a nice signal jamming detection feature that prevents Denial of Service (DoS) attacks.
For additional specifications on the Z-Wave protocol, please visit http://www.z-wave.com.
Bluetooth
Bluetooth is a commonly used wireless technology standard (IEEE 802.15.1) used for data communication over short distances. Bluetooth broadcasts at over 2.4 to 2.485 GHz and can reach up to 100 m but is more commonly used under 10 meters or 30 ft. This book will contain Bluetooth and Bluetooth Low Energy (BLE) testing techniques, as plenty of IoT devices do utilize a form of Bluetooth as a primary means of communication. For additional reading on Bluetooth, visit the following link:
https://www.bluetooth.com/what-is-bluetooth-technology/how-it-works
