Jamming and Anti-Jamming Techniques in Wireless Networks: a Survey
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Int. J. Ad Hoc and Ubiquitous Computing, Vol. x, No. x, xxxx 1 Jamming and Anti-jamming Techniques in Wireless Networks: A Survey Abstract: Because of the proliferation of wireless technologies, jamming in wireless networks has become a major research problem due to the ease in blocking communication in wireless networks. Jamming attacks are a subset of denial of service (DoS) attacks in which malicious nodes block legitimate communication by causing intentional interference in networks. To better understand this problem, we need to discuss and analyze, in detail, various techniques for jamming and anti-jamming in wireless networks. There are two main aspects of jamming techniques in wireless ad hoc networks: types of jammers and placement of jammers for effective jamming. To address jamming problem, various jamming localization, detection and countermeasure mechanisms are studied. Finally, we describe the open issues in this field, such as energy efficient detection scheme and jammer classification. Keywords: Jamming, anti-jamming, wireless networks, classification of jammers, placement of jammers, localizing jammers, detection of jammers, countermeasure for jamming. 1 Introduction in detail different types of jammers, e.g. proactive, reactive, function-specific and hybrid-smart jammers, Wireless networking plays an important role in achieving and the optimal placements of jammers in order to ubiquitous computing where network devices embedded achieve the best jamming affects. Then, we investigate in environments provide continuous connectivity and existing technologies for localizing jammers in networks. services, thus improving human’s quality of life. Finally, we look into how to deal with the jamming However, due to the exposed nature of wireless links, problem. This is the most challenging issue where much current wireless networks can be easily attacked by research has been conducted. For instance, one simple jamming technology. Jamming can cause Denial-of- solution is to apply high transmission power on jammed Service (DoS) problem which may result in several other channels rendering this jamming to be less of a threat. higher-layer security problems, although these are often Another countermeasure of jamming is to use directional not adequately addressed (Wood et al, 2007). antennas instead of omnidirectional antennas. However, none of existing detection or countermeasure methods Jamming in wireless networks is defined as the can address all types of jammers without giving disruption of existing wireless communications by false alarms. Therefore, more research is required for decreasing the signal-to-noise ratio at receiver sides detecting and avoiding different types of wireless network through the transmission of interfering wireless signals. jamming. Jamming is different from regular network interferences Although network jamming is usually considered a because it describes the deliberate use of wireless critical threat, Gollakota and Katabi (2010) proved signals in an attempt to disrupt communications whereas that jamming can be friendly too. They used jamming interference refer to unintentional forms of disruptions. as a defense to counteract eavesdropping attacks. Unintentional interference may be caused by the wireless Particularly, a node will be jamming oneself on its PHY communications among nodes within the same networks (physical) layer so that a snooper cannot demodulate a or other devices (e.g. microwave and remote controller). legitimate signal. Then, receivers jam the transmitted On the other hand, intentional interference is usually signal by flipping certain bits in the packets. Similarly, conducted by an attacker who intends to interrupt or Gollakota and Katabi (2010) use jamming on wireless prevent communications in networks. Jamming can be channels (instead of PHY) to avoid eavesdropper’s done at different levels, from hindering transmission to attack. distorting packets in legitimate communications. There are three main contributions in this article. To understand how a jammer attacks wireless First, from the perspective of an attacker, different types networks and how to avoid jamming to achieve efficient of jammers and their optimal placements are discussed. communication, we investigate three different aspects The classification chart can be used to identify the type of wireless network jamming: 1) types of existing of a particular jammer. Second, from the security point jammers, 2) protocols for localizing jammers and 3) of view, we analyze existing anti-jamming techniques in jamming detection and countermeasure. First, a network detail and classify them into different categories. The can be jammed in various ways using different types summary table can be used to analyze protocols based of jammers. To avoid jamming in networks, it is on different parameters such as network conditions, important to know how a jammer works. So we discuss detection metrics, and countermeasure overhead. Third, 2 we elaborate on key issues of existing countermeasures proactive jammers: constant, deceptive and random. of jamming attacks and point out future research From here on, whenever we use proactive jammers it challenges in avoiding jamming. Existing surveys either can mean all these three. focus on jamming techniques (Pelechrinis et al, 2011) or countermeasures of jammers Mpitziopoulos et al (2009), Constant jammer emits continuous, random bits but our work integrates both topics. without following the CSMA protocol (Xu et al, 2005). The organization of this paper is as follows: According to the CSMA mechanism, a legitimate node Section 2 describes the definitions of jamming attacks, has to sense the status of the wireless medium before classifications of jammers, and jammer-placement transmitting. If the medium is continuously idle for a strategies for effective attacks. In Section 3, we give DCF Interframe Space (DIFS) duration, only then it is the details of how to localize jammers in networks. supposed to transmit a frame. If the channel is found Section 4 describes various protocols for detection busy during the DIFS interval, the station should defer and countermeasures for jamming attacks. It provides its transmission. A constant jammer prevents legitimate analyses and discussions on existing schemes. Critical nodes from communicating with each other by causing issues in existing protocols and research challenges the wireless media to be constantly busy. This type of are described in Section 5. We conclude our work in attack is energy inefficient and easy to detect but is very Section 6. easy to launch and can damage network communications to the point that no one can communicate at any time. 2 Jamming Techniques Deceptive jammer continuously transmits regular packets (Xu et al, 2005) instead of emitting random Jamming makes use of intentional radio interferences bits (as in constant jammer). It deceive other nodes to to harm wireless communications by keeping believe that a legitimate transmission is taking place so communicating medium busy, causing a transmitter to that they remain in receiving states until the jammer is back-off whenever it senses busy wireless medium, or turned off or dies. Compared to a constant jammer, it corrupted signal received at receivers. Jamming mostly is more difficult to detect a deceptive jammer because targets attacks at the physical layer but sometimes it transmits legitimate packets instead of random bits. cross-layer attacks are possible too. In this section, we Similar to the constant jammer, deceptive jammer is also elaborate on various types of jammers and the placement energy inefficient due to the continuous transmission of jammers to maximize the jammed area. but is very easily implemented. 2.1 Types of jammers Random jammer intermittently transmits either random bits or regular packets into networks (Xu et al, Jammers are malicious wireless nodes planted by an 2005). Contrary to the above two jammers, it aims attacker to cause intentional interference in a wireless at saving energy. It continuously switches between network. Depending upon the attack strategy, a jammer two states: sleep phase and jamming phase. It sleeps can either have the same or different capabilities for a certain time of period and then becomes active from legitimate nodes in the network which they are for jamming before returning back to a sleep state. attacking. The jamming effect of a jammer depends on The sleeping and jamming time periods are either its radio transmitter power, location and influence on fixed or random. There is a tradeoff between jamming the network or the targeted node. A jammer may jams a effectiveness and energy saving because it cannot jam network in various ways to make the jamming as effective during its sleeping period. The ratios between sleeping as possible. Basically, a jammer can be either elementary and jamming time can be manipulated to adjust this or advanced depending upon its functionality. For the tradeoff between efficiency and effectiveness. elementary jammers, we divided them into two sub- groups: proactive and reactive. The advanced ones are 2.1.2 Reactive Jammer also classified into two sub-types: function-specific and smart-hybrid. The detailed classification of different Reactive jammer starts jamming only when it observes jammers can be found in Fig. 1. a network activity occurs on a certain channel (Xu et al, 2005). As a result, a reactive jammer targets 2.1.1 Proactive jammer on compromising the reception of a message. It can disrupt both small and large sized packets. Since