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Shivangi Raman et. al. / International Journal of Engineering Science and Technology Vol. 2(5), 2010, 962-969

Wireless sensor networks: A Survey of Intrusions and their Explored Remedies Shivangi Raman1, Amar Prakash2, Kishore Babu Pulla2, Prateek Srivastava2 Ashish Srivastava3, Shveta Singh3 Indian Institute of Information Technology, Allahabad Abstract – On one hand, where we are seeing and experiencing the dilated technologies, the retrospective of the past is giving the researchers a new area to learn and pioneer new dimensions of the same challenges. Wired sensor networks had been a great source of getting the information about a specific object. But with incremental challenges that were posed to the researchers, wireless sensor networks were developed so that the impugnation that had become drawbacks of the wired network system could be dealt with. The upcoming of the wireless sensor network indeed brought with it many advantageous characteristic features, but there were also some vulnerabilities that crept in along with this great development. This paper shall delineate about the various attacks on wireless sensor networks that depict that they still need to be protected to a great extent, and that there is still much room for development of this novel technology that is experiencing its evolution phase. The paper also tells about the different remedies to the vulnerabilities that have been proposed and would analyze some of the solutions contributed by some of the researchers. Keywords: Wireless Sensor Networks, vulnerabilities, attacks, security. I.

INTRODUCTION

The contribution of WSN has been noteworthy in the fields of farming, medical, military and even in the field of geographical discoveries and planet study[1][2]. WSN are used to locate not only the objects whose area of location is known, but also the objects whose location is anticipated to be around a certain domain. WSN have many specific implementations. These specific implementations have their specific problems and their respective attacks because of their own vulnerabilities that are their low battery power, their limited capability of processing and storage which consists of their volatile memory and their limited bandwidth[2][3]. So it becomes necessary for the researchers to know the attacks that can take place due to the increasing number of vulnerabilities. It is also interesting to note that despite the number of vulnerabilities, there are a large number of uses of the WSN, for instance in the military and in the security applications that are brought into use locally[2]. So it is necessary to look into those qualities of the WSN that make it peculiar and still interesting for usage by most scientists concerned with security. These qualities include the ability to sense and process physical environment and information in it in crude form[3]. The basic idea of the sensors is not to measure the quality of any data or storage of data but to actually get dispersed in a certain geographical area and perform tasks in case of certain specific objectivities like surveillance or monitoring or collecting information about the radical changes occurring in the environmental conditions[4]. This sensing of data that is to be performed under the conditions of the environment varies according to the field and magnitude of the work to perform which the WSN have been designed. That is to say that to sense changes in the human body the sensors should be of a different sensitivity and hence sensitivity varies for the different types of geographical environments as well. The communications are being performed by the usage of the transceivers and this has attracted many scientists to study about the WSN[4]. Vulnerability removal has become a great concern for the scientists and researchers worldwide and causes research to move ahead in the field of WSN to combat its problems and make it much more useful. We would therefore discuss the attacks that are posed in the WSN and their possible remedies.

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Shivangi Raman et. al. / International Journal of Engineering Science and Technology Vol. 2(5), 2010, 962-969 Ease of installation and monitoring due to sufficient structural integrity has been provided by the wireless sensor nodes and this has facilitated the wireless sensor nodes to be installed in desired architectures according to the needs of the users. Sensor nodes have larger number of failures due to the lack of synchronization amongst the various nodes and this is the reason why scientists have paid more attention to the problem of synchronization amongst the various nodes. There are synchronization protocols that were introduced in sensor nodes so that various sensor nodes could establish synchronization amongst their neighbours in order to function effectively. In this paper we shall proceed as follows: while Section II gives an overview of the related works, Section III describes the issues of the wireless sensor network security in detail. In Section IV, we will talk about the probable attacks in WSN. Section V would give the solutions to the problems discussed in section IV and finally, in Section VI, we conclude the paper with some of our remarks. II.

RELATED WORKS

A large amount of contribution has been done by the researchers worldwide in the area of WSN. There have been wide number of surveys regarding the energy efficiency of the WSN and regarding the steps and the protocols that have been implemented in order to solve the problem of low energy capability of WSN and the ways to make them more efficient. The major issues in security are confidentiality, integrity, authenticity and availability[3]. While much emphasis has been laid on design of WSN, comparatively minimal emphasis has been laid on security in WSN[4]. Due to the increasing sophistication in the use of WSN, there is also an increasing demand of security measures that need to be deployed in order to secure them. There have been node-replication attacks witnessed in the past. Keeping these sophisticated attacks in mind, Two algorithms regarding the remedies of these attacks were suggested[5]. Their remedy is based upon the properties that arise only through the action of several nodes together. They have suggested Randomized Multicast Algorithm and Line Selected Multicast Algorithm for solving their purpose and controlling the node-replication attacks. Apart from this attack, there have been multiple such attacks that have posed threat to the confidentiality, integrity, authenticity and availability of wireless sensor nodes. These attacks have been witnessed in the different layers of the network like the physical layer, the data link layer and the transport layer[6]. There have been detailed explanations about the attacks like Sybil attack[6][7][8] and denial of service attack (DoS)[6][7] have been given by researchers in which they have given algorithms and protocols as countermeasures against these attacks. Maximum solutions to the attacks in WSN have been found to be based upon cryptographic grounds. There have been various cryptographic techniques and protocols proposed by different researchers. But some of these protocols also have vulnerabilities in them such that they can be exploited by the attackers and hence used for malicious purposes. Most of the researchers have found out that the different attacks take place at different levels. Also, since the present day computers and laptops have got more capacity and better battery power, they are capable of attacking more effectively than the sensor nodes[2]. The defect here lies in the sensor nodes. We could understand that the sensor nodes are very small in size and hence have a comparatively low battery power[1][2][3], small memory size[2] and less processing power[1] that is used to store primarily the information about the nearby sensors including their addresses and the sensor nodes’ own address and cryptographic key. The major problem that might have been realized by the researchers is that according to the use of the field at a particular instant or in a particular domain, the architecture according to which the WSN need to be placed changes. The architecture getting changed according to the changing environment provides heterogeneity to the WSN. This makes it difficult for the scientists to study such an environment and propose a solution that would be viable for many people and processes and be compatible for the works that would be done in future in the field of WSN. This can be verified by the statement of [9][14] which says that the sensor networks are application specific and that the same solution cannot exist for all the problems. Human body that is an extremely complex creation of Nature has a different type of setting and architecture for WSN while if we take the case of military and environmental studies then the architecture of WSN becomes entirely different. In this paper, we analyze the probable attacks and the prevalent counter measures that have been suggested for them in the field of WSN by different researchers.

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Shivangi Raman et. al. / International Journal of Engineering Science and Technology Vol. 2(5), 2010, 962-969 III.

ISSUES IN WIRELESS SENSOR NETWORKS

The WSN are designed to counter four major parameters of security[10]:confidentiality, integrity, availability and authenticity that can be described as follows: A. Confidentiality: This property says that the information should be shared only between the sender and receiver and should not be leaked to or shared with a third party that is not authentic. B. Integrity: The property of integrity defines that integrity of information is said to be maintained only when there is no change in the data either in form or in meaning. C. Availability: Information should be available to the authentic sender and receiver for them to read and process it. D. Authenticity: The information that is produced or is present with the sender and the receiver should be original and correct, that is to say that the information should be authentic or verifiable and hold some meaning. Also, it should be that the information, if derived should be from a source that is dependable and is registered to be non-malicious. The sender should be able to verify the originality of the receiver and vice versa. IV.

ATTACKS IN WIRELESS SENSOR NETWORKS

There are many attacks that have been recognized in WSN till now by the researchers. These attacks can be categorized under various heads so that they can be well understood in future and the problem of identification of attacks under various domains is not faced in future. In one categorization, the attacks have been categorized as inside attacks and outside attacks[2]. Du and Chen have recognized the inside attacks to be much more powerful than the outside attacks. Because the insiders are considered more trustworthy, the inside attackers are difficult to be detected and defended against than the outside attackers. The attackers have different motives for attacking and these motives initiate their malicious behaviour. There are two reasons for the need of data that have been recognized so far[12]: a)

There is some benefit from the data due to which eavesdropping and node-replication can be done and important information carried by the wireless sensor nodes are leaked either by simply reading them or by retrieval of such sensitive data for their malicious use.

b) There is a need for the attacker to interfere with the data that is being carried in the wireless sensor nodes so that the attacker can corrupt the data and not let the data reach the destination for which the data has been made. We need to node that in the first condition dealt with above, the attacker wishes to know the authentic information and then use it for fulfilling his purpose, while in the second condition, the attacker wishes to corrupt the data so that the data received has lost all its parameters of security and is no more correct and believable. Attacks have also been categorized by many researchers according to the OSI layer levels. They have been found to be taking place mainly at the physical, data link (MAC), network, transport and application layers[2][5]. This factor makes the types of attacks more sophisticated and difficult to be detected and defended. Attacks have been recognized by many researchers. These are studied in detail in our paper and described. Attacks have been categorized into two types[11]- invasive and non invasive attacks Invasive attack: Invasive attacks are those attacks that most commonly take place. They may be of the following types: Sybil Attack: The Sybil attack is a kind of invasive attack. This attack has attracted the interest of many researchers and they have worked in the field of defense against the Sybil attack[8][13][15]. The Sybil attack was first recognized by Douceur.

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Shivangi Raman et. al. / International Journal of Engineering Science and Technology Vol. 2(5), 2010, 962-969 He studied this in the context of peer to peer distributed systems. Sybil attack can be defined as “the attack in which a number of legitimate identities and forged identities are used to get an illegitimate entry into the network”. Thus, we can say that the Sybil attack is an attack by which the identities of the nodes that are authentic are misused by the attacker so that he can make unauthentic entries into the network and exploit the nodes. The illegitimate entries are also made by using some forged nodes that is making some nodes through forgery. The Sybil attack causes the degradation of the integrity of data and also increase in the amount of vulnerabilities. This attack is also performed to detect the misbehavior of sensor nodes[13]. Denial of Service Attack: Apart from the Sybil attack, the denial of service attack forms a part of the invasive attacks. The denial of service attack[4][9] is a serious attack that leads to the network breakdown or severe overflow of information in the memory. The denial of service attack is a method of attacking by which the entire service of the wireless sensor nodes is not just intervened by junk information flooding and disruptions caused by them but by the information denial caused by the sudden breakdown of the wireless sensor nodes and hence loss of information flow due to this reason as well. Denial of service attack is a commonly heard attack and hence its devastating properties are well known as compared to the other attacks which people might not have been so well acquainted. Physical layer denial of service attacks could be collision, jamming or exhaustion so that the overall performance of the sensor node is affected that in turn affects the WSN as a whole in an adverse manner. The denial of service attack can be categorized into a large number of attacks. Our main concern is to concentrate upon the attacks that take place in the domain of the wireless sensor networks. Denial of Sleep attack: The denial of sleep attack is an attack that takes place in the wireless sensor networks. This attack was first identified by Stajano and Anderson[22][24]. The attack concentrates upon the energy consumption of the WSN and consumes energy of those parts of the wireless sensor nodes that had consumed less power and were henceforth in standby mode. The attack imposes such a large amount of energy consumption upon the sensor nodes that the entire charge is consumed by the load levied upon the network and the nodes stop working, or, in other words deny their service. The denial of sleep attack has been mainly noticed in WSN and in devices that are designed to work wirelessly like the PDAs, the laptops and other such devices that aim to work with minimal energy consumption in an efficient manner. The low battery power of the wireless sensor nodes and hence, the consumption of this power makes the nodes more susceptible to the vulnerabilities and hence denial of service through denial of sleep. Three methods have been recognized and described in order to discharge the battery power[22][23]: a) Service request power attack: Repeated requests for service are made to the sensor nodes despite no work in the area, and the sensor nodes waste their energy by responding to the requests as and when asked for, thus wasting much of their energy in responding. b) Benign power attack: In this, the victim is made to execute the tasks that require more energy and thus the sensor nodes waste much of their energy in responding to their requests. Despite the job being necessary, it does make a difference if the time consumed to bring the job into effect is much more compared to other jobs and is considered to be an attack if this request is made maliciously. c)

Malignant power attack: In this attack, the program that would replace the entire program of the sensor that works to conserve power of the batteries is attacked. It is replaced by a malicious program that would consume the energy much faster than is expected or needed.

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Shivangi Raman et. al. / International Journal of Engineering Science and Technology Vol. 2(5), 2010, 962-969 Node-replication Attack: The node-replication attack is the attack in which the sensor node at a point that interests the attacker is cloned[11]. This cloned node consists of those characteristic features in it which may be required as basic needs of the sensor node. Also, those characteristic features are also present that make it easier for the node to collect information relevant to the attacker to accomplish his task. The repercussion of the node-replication attack is that there is confusion in the routing of the message and instead of flowing only to the authentic node, the message also flows to the cloned node and gives information to the attacker also without much monitoring or suspicion. One of the major problems is that it is difficult to recognize whether the node is authentic or cloned because both the nodes look exactly similar and the goal of distinguishing between them becomes more and more challenging in case of the node-replication attack. The node-replication attack becomes notably serious when the cloning of the base station takes place but since the base station holds enough significant information about the network and the wireless sensor nodes, it is provided with enough security due to which sometimes its cloning is not possibly easy. The Sybil attack can be compared to the attack in the computer systems by viruses in which the folders of the authentic programs replicate themselves and it is difficult for the end-user to understand if the folders he is accessing are authentic or illegitimate. It becomes too late for the user to guess that an attack has taken place and by the time he comes to know, the entire system gets compromised. In case of Sybil attack, unless and until some recognition mechanisms are applied, it is difficult for the legitimate nodes of the network to decide whether the nodes near them or to whom they are communicating are Sybil nodes or original nodes that are integral part of the network. Routing attack: There can be different types of routing attacks like the sinkhole attack / blackholes or the wormhole attack and the attack that gives false information about routing. Sinkhole Attack / Blackholes: The sinkhole attack[16][17] is an attack in which the attacking node is inserted into the traffic of the network by giving greed to the other nodes that it contains some useful information and allowing its entry. This node then becomes successful in capturing nearly all the data that may be useful for it thereby utilizing the data in a malicious manner. The node is able to capture the information even from those nodes that are distantly placed. Therefore, this attack on the data can be considered as a serious attack where all sensitive data can be successfully sniffed from the network and hence eavesdropped upon thus affecting the parameters of confidentiality and integrity of the information. Once the two parameters of security are compromised, it can be well understood that the security as a whole has been compromised with. Wormhole Attack: In wormhole attack, the adversary takes the message from an area and displays it in another area. This makes the adversary eavesdrop upon useful information and display it in another area, thus redirecting the message traffic[18]. The packets of information are tunneled and then displayed[19].

a) Non-Invasive Attack: The non-invasive attacks, as mentioned earlier, deal with the attacks that take place at the MAC layer and are such attacks that are rarely observed. Non-invasive attacks usually take place at the link layer. The security therefore becomes a major concern for the network engineers if the WSNs have a possible vulnerability at the link layer due to which an attack is expected at the MAC protocol of link layer.

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Shivangi Raman et. al. / International Journal of Engineering Science and Technology Vol. 2(5), 2010, 962-969 V.

EXISTING SOLUTIONS TO THE EXISTING ATTACKS

There have been various solutions proposed to tackle the problem of attacks over wireless sensor networks, most significant of them being the cryptographic and protocol based solutions to the attack problems of WSNs. These solutions have been proposed according to the various problems that have been faced while making the wireless sensor networks secure and suitable for sending information as well as accumulation of information in order to resolve the serious problem of redundancy that troubles most researchers and The proposed protocols can be categorized according to the different attacks. Deluge: The denial of service attack has been tackled by using the protocol Deluge and modifying it to some extent in. Modified deluge uses a method that is more energy efficient and also saves the integrity and authenticity of the information. Deluge has been used to solve the problems of security and energy efficiency. Also, it is being deployed in TinyOS distributions, so its use has gained impetus. SDD and CDD: Two specific protocols were decided for capture detection: the Simple Distributed Detection protocol (SDD) that implements False Alarm Neutralization (FAN) mechanism and the Cooperative Distributed Detection (CDD)[20] in which network mobility is given impetus to make node capture detection improve from its current status. CDD also increasingly depicts node non cooperation to improve node capture detection. SPINS: Another piece of work to safeguard wireless sensor networks against attacks is SPINS that consists of two protocols: SNEP (Sensor Network Encryption Protocol) and µTesla[10]. SNEP provides the information with the characteristic features and parameters of security like integrity, authentication and freshness of information that ensures confidentiality while the µTesla ensures that there is authenticated broadcast of the message. Checksum: For authentication, the MAC protocol is used that ensures that the checksum calculated at the sender’s end is the same as the checksum calculated at the receiver’s end so that it becomes sure that the message has not been tampered with and that the integrity of the message is maintained. The cryptographic algorithms when used and the network layer protocols when deployed ensure the privacy of the information. State Based Key Hop Protocol (SBKHP): The state based key hop protocol[21] is a protocol that provides a strong method of encryption for the devices that work with battery power. The SBKHP is comparatively cheaper than wired equivalent privacy (WEP). It is also efficient because it does not have the vulnerabilities that are contained in the WEP that is deployed in IEEE 802.11. The SBKHP can be efficiently used in the WSN as well. This is because the wireless sensor nodes work with the use of battery and the protocol has been designed to be helpful for mainly such equipments. The SBKHP is much helpful for the control of the denial of service attack. The cipher stream changes as soon as the packet is acknowledged and this saves the packet from being forged or maliciously resent. The forged packet shall not match with the originally received packet and this shall prevent the duplicate packets from increasing the traffic in the network. RC4’s vulnerabilities that were prevalent in the wired equivalent privacy protocol (WEP) have been removed while proposing the SBKHP. There are algorithms also that have been suggested in order to prevent the distributed node-replication attacks in the wireless sensor nodes of the WSNs[5]. The node replication attack, as discussed previously in our paper, is an attack

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Shivangi Raman et. al. / International Journal of Engineering Science and Technology Vol. 2(5), 2010, 962-969 in which an authentic node’s replica is made by the attacker and this replica gets a copy of the authentic information that is being sent via the sensor nodes from and to the base station. The proposed algorithms are Randomized Multicast algorithm and Line Select Multicast Algorithm. The Line Select Multicast Algorithm uses the topology of the network in order to detect the replicated nodes while the Randomize Multicast Algorithm uses the information from the distributed nodes in order to detect the replicated nodes so that the node replication attacks can be prevented and/or detected even if it takes place in a distributed manner. There have been two methods proposed by researchers for combating the denial of sleep attack in sensor networks[25]: i)

Identifying Jamming and Mitigating it

ii) Protection against broadcast attacks by first authenticating and then sending the message to the different sensor nodes that are peers to the sending sensor node. VI.

CONCLUSION

With this paper, we have tried to evaluate the ongoing scenario of wireless sensor network security. We studied the wireless sensor networks in detail, mainly trying to concentrate on the different attacks prevalent in the realm of WSN and the different protocols and algorithms that can counter these attacks. VII.

FUTURE WORK

Still there are many attacks and vulnerabilities in other areas like water and human body where sensor networks are deployed and which are out of our scope of study and out of the scope of this paper. There can be a large amount of further research in the areas. For instance, the vulnerabilities of the various sensor network protocols that are efficient at solving one attack but fail to counteract upon the other attacks can be comparatively studied. Their vulnerabilities can be removed so that they can be efficiently deployed as a remedy for combating other attacks as well. REFERENCES [1] [2] [3] [4] [5] [6] [7]

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Shivangi Raman et. al. / International Journal of Engineering Science and Technology Vol. 2(5), 2010, 962-969 [18] Stefan Ransom, Dennis Pfisterer, Stefan Fischer, “Comprehensible security synthesis for wireless sensor networks” in ACM Proceedings for 3rd international workshop on Middleware for sensor networks, December 2008. [19] John Paul Walters, Zhenqiang Liang, Weisong Shi, Vipin Chaudhary, “Wireless Sensor Network Security: A Survey” in Security in Distributed, Grid and Pervasive Computing, Auerbach Publications, CRC Press, 2006. [20] Mauro Conti, Roberto Di Pietro, Luigi Mancini and Alessandro Mei, “Emergent Properties: Detection of Node-Capture Attack in Mobile Wireless Sensor Networks” in Proceedings of the first ACM conference on Wireless network security pp 214-219, 2008. [21] Stephen Michell and Kannan Srinivasan, “State Based Key Hop Protocol: A Lightweight Security Protocol for Wireless Networks” in Proceedings of the 1st ACM international workshop on Performance evaluation of wireless ad hoc, sensor, and ubiquitous networks, pp-112-118, 2004. [22] Michael Brownfield, Yatharth Gupta, Nathaniel Davis, “Wireless Sensor Network Denial of Sleep Attack” in Proceedings of the 2005 IEEE Workshop on Information Assurance and Security, United States Military Academy, West Point, New York, 2005, pp-356-364. [23] Thomas Martin, Michael Hsiao, Dong Ya, Jayan Krishnaswami, “Denial-of-service-attacks on Battery-powered Mobile Computers” in Proceedings of the Second IEEE Annual Conference on Pervasive Computing and Communications 2004, PerCom 2004, pp-309318. [24] David R. Raymond and Scott F. Midkiff, “Clustered Adaptive Rate Limiting: Defeating Denial-of-Sleep Attacks in Wireless Sensor Networks” in Military Communications Conference 2007, MILCOM, IEEE, pp-1-7. [25] David Raymond, Randy Merchany, Michael Brownfield and Scott Midkiff, “Effect of Denial of Sleep Attacks on Wireless Sensor Network MAC protocols” in Proceedings of the 2006 IEEE Workshop on Information Assurance, United States Military Academy, West Point, New York, 2006, pp-297-304.

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