I. INTRODUCTION:

In the 1970s, the earliest systems were mainly wired and small, while in military and industrial applications, the new concept of networks & distributed sensors resulted in their use. In the 1990s, when VLSI design became feasible for wireless technologies and low power, the researchers first began to think about a wireless sensor application and to inspect large WSN.[1]

The continuous technological progress enables us to look at the future when many energy-efficient and cheap SNs are deployed densely in the physical environment and are all working together to form a WSN. These WSN's broad application areas include remote environmental monitoring, infrastructure health monitoring, tracking the target, home and office automation and safety, public security, event-detection, identification of event boundaries, medicine, transport, etc.[2]

A large number of sensor nodes (SNs) with poor processing power, a radio transceiver and restricted storage with a battery restrict are put in an unattended and hostile environment through the use of WSNs. SN is able to measure and manipulate and communicates with other SNs. The SN then establishes an ad-hoc network without any framework. SNs are prone to various kinds of attacks since they are often deployed in severe unattended conditions. [3]

II. ARCHITECTURE OF WSN:

As shown in figure 2.1 [4], classical WSN is made up of a considerable number of SNs that mutually work together to complete a common task. Generally, each SN sends the sensed data through wireless medium to a base station or sink node via gateway SN.

Figure 2.1 Classical Wireless Sensor Network [4]

As shown in Figure 2.2 [5], Following major elements constitute to form a typical wireless SN:

· Energy Efficient Processor

· Limited Memory / Storage

· Low Range Radio Transceivers

· Various Sensors

· Power Sources

Figure 2.2 Typical Wireless Sensor Node[5]

III. CONSTRAINTS ON WSN:

According to the limited and confined capacity of the SNs, the computing ability and storage potential of electricity and the frequency of contact of WSN are very reduced. The operational mode of WSN is of a kind from the wired network. Therefore we should, first of all, consider all the factors of the restrictions while debating the appropriate WSN security mechanism so that you can find out about the safety mechanism suitable for WSN [6]. Following is the list of inherent limitations of WSN that makes it more complicated to design your safety procedures.

A. Node Constraints:

A standard SN processor with a radio frequency of 48 MHz, 4 KB RAM and a 128 KB flash with a radio frequency of 196 KHz. Heterogeneity of SNs is an additional problem that prevents a safety solution. SNs are installed in environments that may be highly sensitive to physical damage because of the random deployment.

B. Network Constraints:

With SN limits and unreliable wireless devices, sensor networks all have MANET's drawbacks where physical infrastructure is not established.

C. Physical Constraints:

Sensor networks in open and hostile environments are highly susceptible to physical damage and capture in many applications. The physical safeguarding of SNs by tamper evidence increases node costs.

IV. SECURITY GOALS IN WSN:

Based on the constraints of WSN, we determine that security goals can becategorized as primary and secondary. The key aims are traditional security objectives, i.e., Confidentiality, Integrity, Authentication, and Availability (CIAA)[7]. The secondary targets are the freshness of data, self-organization, time synchronization, secure Localization, robustness, and access control [8].

A. Confidentiality applies to a passive attacker's ability to cover up the message so that the communication on WSN stays hidden.

B. Integrity is the ability to ensure the user does not modify, alter, or modify the message while on the network communication.

C. Authentication is a need to test the authenticity of its sources if the message comes from a node it appears to be from.

D. Availability is going to determine if a node has resource access permission, and the network can communicate messages for the node.

E. Data Freshness: It ensures no replay of old messages. While classification and correct information are guaranteed, the freshness of every word must still be ensured.

F. Time synchronization: Time synchronization aims to equalize local times for all network nodes,where necessary. Since the device power, bandwidth, energy sources and storage capacity of WSNs is reduced. The synchronization of the network cannot be affected by traditional time syncing algorithms such as the network time protocol and the global positioning system.

G. Self Organization: A remote sensor network is a specially designed device periodically that demands that every sensor nodeis safe, adaptable enough to act naturally, according to different circumstances and to self-structure. This functionality conveys an extraordinary measure for the reliability of remote sensors.

H. Secure Localization: A WSN to identify a shortage requires precise region statistics to show the location of a deficiency often. The effectiveness of a WSN relies on its capacity to senses data correctly and therefore identifies any SN in the framework.

I. Robustness: WSN is highly dynamic and unpredictable, as the topology of the network varies, and node leaves or enters continuously. WSN should, therefore, be highly adaptable to a range of security threats. The performance should still minimize the impact, even if a particular attack succeeds.

J. Access Control: Access control means that users who can access WSN can be identified to ensure their authority. Access control determines which network resources can be obtained, which system resources, and how these system resources can be used.

V. SECURITY CHALLENGES IN WSN:

The researchers will understand the security issues before implementing WSN safety schemes focused on the above objectives. The existence of massive, ad-hoc WSN presents significant challenges during the creation of the security mechanism. A WSN is a first network that has several limitations as compared to a traditional computer network [9].

A. Wireless Medium:

The wireless medium is insecure due to its broadcast nature which make seaves dropping easy. Any communication can be simply intercepted, altered, or replayed by an attacker. The wireless medium allows an intruder to effortlessly intercept valid packets and inject malicious ones without any trouble. Although this problem is not exclusive forWSN, traditional countermeasures must be adapted to perform on WSN efficiently.

B. Ad-Hoc Deployment:

WSN's ad-hoc nature means that the framework is not fully established. It is possible to deploy SNs at random, so nothing about topology is known before deployment. Since the SNs will malfunction or be replaced, the WSN must support its own setup. In this chaotic and complex environment, the protection system must be operational.

C. Harsh Environment:

The harsh environment in which motes work is the next obstacle. SNs face the possibility that adversaries will damage or seize them. To security researchers, the extremely hostile environment is a major challenge.

D. Massive Scale:

The enormous scale of WSN poses a major safety obstacle. It has proved to be an important task only to connect tens of hundreds or thousands of nodes.

VI. SECURITY ISSUES IN WSN:

In general, attacks are commonly categorized in 2 groups,

i.e. active attacks and passive attacks. All attacks are discussed in depth in this paper. WSNs are most vulnerable to security threats while transmitting through channels because of their broadcasting nature [10].

A. Passive Attacks: Passive attack is called listening and monitoring of the transmission channel by unauthorized persons. Some of the most common passive attacks against privacy are:

1. Eavesdropping: This is the most common sensor confidentiality attack. By snooping into the transmitted data, the attacker will easily find out the contact information.

2 Traffic Analysis: There is still a high probability analysis of communication patterns, even if the messages are encrypted before transmission. Knot activities can potentially reveal sufficient data to allow a malicious damage to the WSN by an intruder.

3 Camouflage Adversaries: Adversary can add or compromise their malicious nodes in the WSN. After this, the malicious nodes that have been infected will serve as a standard node for analyzing the data traffic, collect data packets and misroute them.

B. Active Attacks: The unauthorized person not only monitors and listens to data traffic but also changes the transmission channel data stream called an active attack. The attacks below are real in nature.

1. Routing Attacks: Routing attack is also the attack that works on the network layer. The attacks that occur during the data packets are as follows.

a. Attacks on Information in transit: Each SN tracks changes of particular values or parameters in a WSN and reports any unusual behavior in compliance with its specifications to the sink node. The message can be detected, tampered, replayed or even discarded during transit during the sending of the study. As wireless transmission is susceptible to eavesdropping, any intruder can easily monitor the traffic flow and get into action to intercept, interrupt, modify or fabricate data packets thus, supply incorrect information to the sink node or base station.

i. Interruption: If the contact connection in WSN is lost or inaccessible, there is an interruption. E.g. node capture, message leakage, malicious code addition are examples of this type of attack.

ii. Interception: The interception takes place when an attacker has affected WSN, when the intruders get unauthorized access to or data from the SN. The node capture attacks are an example of this type of threat.

iii. Modification: Modification occurs when an unauthorized person not only accesses, but also tamps data, such as changing the transmitted data packets.

iv. Fabrication: Fabrication happens when an attacker injects fake data and compromise the trust of the information. For example, a network is filled with fake data triggering a Denial of Service (DOS) attack.

b. Blackhole attack: A malicious SN is beginning to act as a black hole in order to attract all the data traffic in the WSN. So even SNs which are very far from base stations can easily be affected by that attack. Figure 6.3 [4] shows the blackhole / sinkhole attack conceptual view[11].

Figure 6.3 Blackhole/Sinkhole Attack [4]

c. Wormholes Attacks:

Wormhole Attack is a serious attack where an opponent stores the packets at one place in the network and tunnels them to another part of the system. Figure 6.4 [4] shows a wormhole attack scenario. When a node B broadcasts a routing request packet, the modifying node S receives this packet and transmits it in its nearby node Z. Every neighboring node which receives this replayed packet shall be considered in Node B and shall make Node B as its parent. Therefore, even if the victims node Z is not a B-node, the opposing node S can mislead them that B is just a single hop away, which finally creates a wormhole in WSN[12].

Figure 6.4 Wormhole Attacks[4]

d. Sybil Attack:

Each SN may have to work together to perform a common function, for which subtasks and informations can be shared between themselves. In such a case, an SN may say that the identities of other nearby knot, as shown in figure 6.5 [5], are more than one node. This type will use the attack in the form of a node which forges the identities of the Sybil attack. Sybil attack attempts to degrade the integrity in the distributed algorithm of data, protection and resource use in the WSN[13].

Figure 6.5 Sybil Attack [5]

e. Selective Forwarding:

Only a specific number of packets may be dropped by a compromise SN. In combination with another attack, it is particularly efficient to gather more data traffic via the SN. With WSN, all received packets were presumed to genuinely be forwarded by SN. Nonetheless, a malicious SN can refuse to forward packets; the neighboring SNs may begin to provide the message via another path.

f. HELLO, flood attacks:

An intruder sends or replays HELLO routing protocol packets from one node to another repeatedly to waste more SN power. HELLO packets are used to flood the WSN with HELLO packets in this attack.

2. Denial of Services:

Denial-of-Service (DoS) is a kind of attack in which the attacker wants to prevent its intended users from accessing network resources. One of the most common approaches to such an attack is to overflow the network with unwanted, irresistible numbers of packets, which therefore saturate the bandwidth of the target system.

3. Node Subversion:

SN selection may reveal its information, including its encryption keys, thereby affecting the safety of the entire WSN. Each single SN can be obtained and an intruder can access the key information that is stored on the SN.

4. Node Malfunction:

A malfunctioning node can produce imprecise sensed data, particularly when a data-aggregation node, such as a cluster head, can compromise WSN's integrity.

5. Node Outage:

Network failure is the case when a network stops working. If a cluster head stops functioning, it should design the WSN protocols so strong that it should provide an alternative track to minimize the effects of node failures.

6. Physical Attacks:

Unlike most of the above attacks, physical attack completely kills SN and the damage is therefore irreversible. The attacker, for instance, can steal cryptographic keys, alter the associated SN circuitry, manipulate the programming in the SN or, as a consequence of the adversary, replace it with malicious SN.

7. Message Corruption:

This happens when a data packet is changed by the attacker in the message content and its validity is jeopardized.

8. False-Node:

A malicious node involves an attacker adding an SN which eventually causes the malicious data to be injected. A node that feeds fake data or limits exact data flow can be added by an attacker in the WSN. The insertion of a malicious node into WSN represents one of the most dangerous attacks.

9. Node Replication Attacks:

In theory, replicating a node is quite easy. An adversary tries to connect a SN to an existing WSN by copying the node ID of the original SN. A replicated node in this strategy will seriously disrupt the output of WSN. It can easily misunderstand or misrepresent the message.

10. Passive Information Gathering:

If there is no encryption techniques applied to transferred data, a skilled attacked person with some resources can easy collect WSN information. Robust encryption algorithms should therefore be used to reduce the risk of passive data collection attacks.

VII. LITERATURE REVIEW:

Author	Methods
Xuran Li et. al.	This paper [14] suggestes a new research model to analyze the Wireless Internet of Things (WnoT) eavesdropping attacks. Includes path degradation, shade fading and the Rayleigh fading effect and different channel conditions, including WNoT's eavesdroppers.
Daehee Kim et. al.	This article [15] proposes a fully distributed, efficient system that randomly overrides the processing capability of new PKC request messages. The device is not only immune, but also energy efficient, to PKC-based denial of service attacks.
Sachin D. Babar et. al.	This paper [16] provides the Cluster Head Intelligent Attack (CH) jamming in the cluster- based network. It also indicates the solution to combat the attack during contact between and inside the clusters.
Bin TIANet. al.	In this paper [17] the author has suggested a method for identification of Sybil in this paper based on the context of wired networks. The detection Sybil proposed attacks via the location of anchor nodes.
Manju.V.C et. al.	This article [18] explores the S-MAC and T- MAC features that make them vulnerable to sleep denial. The proposed two-part approach is to defend a sleep denial. Network organization. Selective level authentication.
Chen Chen et. al.	This paper [19], a scheme is proposed using a fake schedule changeover with a RSSI measuring aid based on an analysis of the trend and techniques of denial-of-sleep attacks in the WSN.
KaipingXu e et. al.	This paper [20] presents a critical efficient distribution mechanism for wireless networks based on hierarchical topology, which can withstand the attack by nodes, with a change in the safety of the original scheme.
Eugene Y. Vasserman et. al.	This article [21] addresses attacks on the routing protocol layer that permanently deactivate networks by fastly draining battery power of nodes.
Lingxuan Hu et. al.	In this paper [22] a cooperative protocol in which nodes share directional information is presented to avoid masquerading wormhole endpoints as false neighbours.
Majid Alotaibi	In this paper [23] Hamming residue method (HRM) is presented to reduce malicious attacks. A new security codeword is generated with each node.
Hong-Ning Dai et. al.	The author in this paper [24] has proposed a model for the analysis of the probability of droppings in both single hopWSNs and multi- hop WSNs with omni-directional antennas.
NazliSiasi et. al.	In this paper[25] a selective forwarding attack is proposed to be solved at near-instantaneous recovery times in wireless sensor network networks using the LEACH protocol. The identification and efficient recuperations are focused on the coding of diversity networks.

VIII. CONCLUSION:

In recent years, security in WSNs has received great attention. System protection for such systems is more difficult than traditional networks due to extreme power limitations and complex deployment conditions for WSNs. Infrastructureless components can easily become an attacking point. In order to achieve security and privacy, it is therefore important to incorporate safety into every aspect. Although each of the security solutions can be used to effectively securing a WSN, at present there is no solution that can be linked to an application to provide all the security primitives needed.

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Received on 20.05.2020 Accepted on 18.06.2020

Research J. Engineering and Tech. 2020;11(2):62-68.

DOI: 10.5958/2321-581X.2020.00012.4