Wireless Sensor Networks are a subset of ad hoc networks. Their unique characteristics are smaller node size, high node density, unattended operation in remote areas. Dynamic topology and wireless communication make them vulnerable to numerous types of attacks. In addition to that, memory, processing, and energy constraint make it difficult to incorporate compute-intensive security solutions in these networks. Existing solutions for developing cost and energy efficient algorithms do not fit the security parameters for these resource constrained networks. As a result, these networks remain vulnerable to several types of attacks. This chapter presents a survey of various attacks at the different layers of WSN protocol stack, their detection, and countermeasures. Although every layer of the stack has its own security challenges, the network layer is most vulnerable to many security attacks because it provides an excellent basis for traffic monitoring activities, which helps the attacker form a strategy to perform the attack. The most common attacks on this layer are the Sybil attack, selective forwarding attack, wormhole attack, sinkhole attack, etc. This survey provides a comprehensive view of present attacking strategies to disrupt the normal functioning of WSN.
TopIntroduction
In the 1980’s when Defense Advanced Research Project Agency (DARPA) started its research on Distributed Sensor Network (DSN), the size of the sensors were large (i.e- shoe-box and up), which limited the potential application of these networks. Further in these DSNs the sensor nodes were using wired connectivity among them. Recent technological advancements have caused a significant shift in WSN (Matin and Islam, 2012; Wang and Balasingam, 2010) and nowadays, sensor nodes are much smaller in size (pack of cards or dust particle), distributed in nature and communicate with each other using wireless medium only. In a typical Wireless Sensor Network, sensor nodes sense the physical phenomenon, compute some result and transfer the result to the base station (BS), which is connected to the end user via internet (Akyildiz, Sankarasubramaniam, & Cayirci, 2002; Ahem, 2004; Elson & Estrin, 200) as shown in Figure 1.
Figure 1. A typical Wireless Sensor Network
The hardware component of a sensor node include one or more sensors to sense the physical phenomenon (e.g. Light, temperature, pressure, etc.), transceiver for wireless communication, a processing unit to convert sensed data into suitable format for transmission, used to log the sensed data. Batteries act as power source. Figure 2 shows the schematic diagram of a sensor node.
Figure 2. Schematic diagram of a sensor node
WSN has been viewed as one of the most emerging technology for the 21’st century (Coy et al, 1999). Upcoming companies like Crossbow, Smart Dust Networks, Berkley etc. are also working hard in accelerating the commercialization of WSN by reducing the chip size (Coin size). Figure 3 shows the photographs of some modern sensor nodes.
Figure 3. Current sensor node hardware. TelosB mote by Crossbow (“Telosb Mote”, 2012), a coin-size mote by Smart Dust (“Smart Dust Mote”, 2012) and Tmote Sky by Moteiv (“Tmote Sky”, 2012)
The sensor node senses the required phenomena and sends the data to the base station or sink by a multihop infrastructure less architecture. The sink may communicate to the end user via internet or satellite. Due to wireless nature of media all the security loopholes of any wireless network is inherent in sensor networks. Their unattended deployment in hostile environment and scarcity of resources makes them more vulnerable to physical attacks (Becher, Benenson & Dornseif, 2006). Their low cost allows user to deploy them in large amount but their limited processing capability, less storage and low power poses another challenge to use any of the existing security protocol of ad-hoc networks with them. Most of the researchers have tried to develop different security protocols for such resource constraint networks.
This chapter surveys various attacks and it’s countermeasures based on protocol stack, in WSN.
The rest of the chapter is organized as follows: After discussing applications, challenges of WSN are presented followed by taxonomy of various attacks in WSN protocol stack. Next, we discuss security attacks and its countermeasures in the physical layer, followed by attacks and countermeasures at MAC layer. This is subsequently followed by a discussion on attacks and detection schemes in the network layer, transport layer and application layer. While enumerating various possible attacks, the chapter provides a detailed discussion on various existing security mechanisms and protocols to defend against and wherever possible prevent the possible attacks. A number of future research issues and open problems are also mentioned before the chapter is finally concluded.