# Comprehensive Study of IoT Vulnerabilities and Countermeasures
## 3 IoT Vulnerability Layers
### Network Vulnerabilities
#### 3.3.2 Wireless Sensor Networks  
A wireless sensor network (WSN) comprises spatially distributed sensors that transmit data wirelessly, forming the backbone of many IoT deployments. These networks span a diverse array of protocols--Zigbee, Z-Wave, GPS, 5G, and more--each tailored to specific sensing and communication needs. This versatility underpins the ubiquity of IoT devices, yet it also amplifies their exposure to attack. For clarity, this paper separates WiFi and Ethernet-based networks from WSNs, given the distinct breadth of vulnerabilities in the former. Within WSNs, Denial of Service (DoS) attacks present a significant threat, with their taxonomy delineated in Figure 11, encompassing a spectrum of tactics beyond those seen in traditional networking. Figure 11 reveals a DoS framework tailored to WSNs, incorporating WiFi and Ethernet threats while introducing unique exploits. At the physical layer, jamming and node tampering reign as the most prevalent attacks. An adversary might jam a Zigbee network with interference, blocking nodes from transmitting or physically compromise a sensor to extract--or alter--its firmware [92]. Inserting a malicious node amplifies this, severing legitimate connections by drowning out signals. To mitigate jamming, frequency hopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS) can be implemented to make it harder for attackers to effectively disrupt communication [93; 94]. Additionally, tamper-resistant hardware with physical shielding can reduce the risk of unauthorized access to sensors. Figure 10: WiFi over-the-air attack. This image has been completely re-modified; however, the idea of the image was inspired by [89]. Link-layer attacks shift to subtler sabotage; a rogue node might masquerade as trustworthy, exhaust neighbors with incessant requests, or induce collisions to crash nodes via errors [92]. At the network layer, flooding mirrors WiFi-style down outs, overwhelming routing paths with traffic. The transport layer hosts flooding--swamping nodes with fake peers--and desynchronization, where message timing is scrambled, leaving nodes out of sync [92]. These attacks can be mitigated by implementing rate limiting, packet authentication, and anomaly detection algorithms that identify excessive traffic patterns or suspicious communication behavior. Beyond DoS, WSNs face routing-centric threats like the black hole attack, depicted in Figure 12. Here, a malicious node lures others to redirect data through it, acting as a sink that absorbs--or discards--transmissions, halting network flow [95; 96]. Closely related to this is the wormhole attack, shown in Figure 13, where data are tunneled between two colluding nodes--say, from node A to node B--bypassing the intended routes [97; 98]. This rerouting distorts network topology, granting attackers control over data paths. To mitigate black hole and wormhole attacks, secure routing protocols such as Secure Efficient Ad hoc Distance vector (SEAD) and Ad hoc On-Demand Distance Vector (AODV) with authentication mechanisms can help verify node identities before allowing data redirection [99; 100; 101]. Time-based packet verification methods can also be implemented to detect unusual delays indicative of wormhole behavior. Figure 13 illustrates how wormhole nodes--A and B--siphon data through a tunnel, manipulating its flow. This attack manifests in four modes as follows: Packet encapsulation compresses data between nodes, evading hop-count increments typical in WSN routing [98]. Packet relay mode uses any node as a launch point, relaying traffic to disrupt paths [98]. Out-of-band channel attacks rely on a single high-power node to redirect packets via an  
Figure 11: Wireless sensor networks DoS attacks. This image has been completely re-modified; however, the idea of the image was inspired by [92]. Figure 12: Blackhole attack. This image has been completely re-modified; however, the idea of the image was inspired by [102]. external link [98].