# A Survey of Internet of Things (IoT) Authentication Schemes +
## 3 Security Issues in IoT
### Security Challenges in IoT Layers
#### 3.2.2 Network Layer Security Issues and Requirements  
The network layer is in charge of the diffusion of data from the perception layer to the application layer. This is where data routing occurs as well as the primary data analysis. In this layer, several network technologies are used such as the different technologies for mobile communication generations (2G, 3G, 4G and 5G) and wireless networks (Bluetooth, WiMAX, WiFi, LoRaWAN, etc.).  
Several attacks and risks on the network layer are identified:  
1. _Man-in-the-Middle (MITM)_: According to McAfee [6], the most recurrent attacks are Denial of Service (DoS) and Man In the Browser (MITB) attacks. This latter, along with the Secure Socket Layer (SSL) attack, which enables attackers to listen to traffic, intercept it, and spoof both ends of the data, constitute the MITM attack [48; 49].
2. _Denial of Service (DoS)_: This type of attacks occurs also at the network layer by jamming the transmission of radio signals, using a fake node, affecting the transmission or routing of data between nodes [50; 51].
3. _Eavesdropping/sniffing_: This type of passive attacks gives the intruder the ability to listen to the private communication over the communication link [52]. The intruder might be able to extract useful information such as usernames and passwords, node identification or node configuration, which could lead to other types of attacks, e.g., fake node, replay attack, etc.
4. _Routing attacks_: This type of attacks affects how the messages or data are routed. The intruder spoofs, redirects, misdirects or even drops packets at the network layer. The following specific attacks could be considered: 1. Black Hole: It can also be considered as a DoS attack, in which the intruder uses a fake node that welcomes all traffic by asserting that it has the shortest path. As a result, all traffic will be redirected to the fake node that has the ability to redirect them to a proxy server or even drop them [53]. 2. Gray Hole: This type of attacks is similar to the black hole attack but instead of dropping all the packets, it only drops selected ones [54; 55]. 3. Worm Hole: In this type of attacks, the intruder creates a connection between two points in the network by either controlling at least two nodes of the network or adding new fake nodes to the network. After forming the link, the intruder collects data from one end and replays them to the other end [56; 57]. 4. Hello Flood: The aim of the attacker in this type of attacks is to consume the power of nodes in the system by broadcasting Hello request packets by a fake node to influence all the nodes in the system that they are in the same range, thus causing each one to send packetsto its neighbor causing a huge traffic in the network [58; 59; 60]. (hello messages are defined in some routing protocols, so that nodes announce themselves to their neighbors.)
* Sybil: In this attack, a fake node presents multiple identities, thus it can control a considerable part of the framework by being in different places within the network at the same time. When I many sybil nodes are within the same network, they will then send a large amount of information denying the normal nodes from using the network [61].  
These potential attacks at the network layer (wired or wireless) lead to the definition of the following security requirements: hop-to-hop encryption, point-to-point authentication, key agreement and management, security routing and intrusion detection [62].