Wireless Sensor Network (WSN) is a promising technology that has attracted the interest of research in the last decade. Security is one of the fundamental issues in sensor networks since sensor nodes are very resource constrained. An attacker may modify, insert, and delete new hardware and software components to the system where a single node, a specific part of the sensing area, and the whole network may become inoperable. Thus, the design of early attack detection and defense mechanisms must be carefully considered. In this chapter, the authors survey attacks and their defense mechanisms in WSNs. Attacks are categorized according to the related protocol layer. They also investigate the open research issues and emerging technologies on security in WSNs.
TopIntroduction
In the last few years, with the advancements in technology, new device designs that are different than the personal computers, laptops and servers have been introduced and used extensively all over the world. These devices are smaller and cheaper, and use less energy than the ordinary designs. Besides, they are designed on the integrated circuits having a low power communication unit. Their design techniques provide the use of Wireless Sensor Networks (WSNs). A microprocessor of a sensor node not only includes volatile memory and processor but also includes non-volatile memory, digital to analog converter, analog to digital converter, universal asynchronous receiver transmitter and interrupt controller interfaces. In addition, low range radio frequency, infra-red and optical communication techniques are used in these nodes. Moreover nodes can sense heat, light, acceleration and chemical contaminants from the environment and can send these information through a wireless communication channel.
WSNs are ad hoc networks that are composed of hundreds to thousands self-organizing sensor nodes. An example WSN is given in Figure 1. Each sensor node may collect information from the sensing area and relay its data to the sink node on a multi-hop path. Sink is a gateway node that collects data from the other nodes located on sensing area and aggregates the delivered data. Sink node may communicate with a repository in order to deliver its collected data. The data repository may store data in various forms in order to give query service to the users through Internet.
Figure 1. WSN integrated information system example
WSNs have many application areas in today’s world (Garcia-Hernandez, 2007). One of the most important applications is habitat monitoring. In the Great Duck Island (GDI) application, the life cycle of storm petrel birds are monitored by researchers from UCB and Intel (Mainwaring, 2002). In the PODS application (Biagioni, 2002) developed in Hawaii University, some endangered plant species are investigated. ALERT system is developed for the early detection of flood threat by measuring water level, heat and wind power. Another application area of WSN is patient’s health monitoring. Schwiebert (2001) developed a system for blind people to sense the objects in their environment. Remote patient monitoring and management of drug usage are the other type of health-based applications (Akyildiz, 2002). Another WSN application is home and office deployment. Srivastava (2001) developed a kinder garden project for educating children.
An attack on a WSN can be defined as a bad behavior by a single node, malicious invasion on a specific part of the sensing area, or an action to defect the operation of the whole system (Sokullu, 2008). The adversary is used synonymously with the attacker which is the originator of an attack (Wood, 2004). The adversary attacks to the network with the aim of damaging a single or group of nodes in order to gain more selfish benefits on the related services than the other nodes of the WSN (Sokullu, 2009). The attacker may exploit protocol weakness to gain network resources, may create fake packets, may overwhelm the nodes, may behave strangely like switching between on and off status or even may simply reach and reprogram the sensor nodes. The basic feature of these attacks is that they are entirely unpredictable (Radosavac, 2007). Identification and investigation of these attacks are very important to design defense mechanisms or counterattacks.
Today, WSNs in various topologies are used with many different applications that are integrated into kinds of Information Systems. To us, the security of those Information Systems is strongly associated with the security of the WSN used within. For that reason, we believe that a chapter covering the WSN attacks and their defense mechanisms as a detailed survey on the security in WSNs would be properly related to the content of Secure Information Systems.