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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>A lightweight Anomaly based DDoS flood attack detection for Internet of vehicles</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Kuthada Mohan Sai</string-name>
          <email>mohankuthada@gmail.com</email>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff2">2</xref>
          <xref ref-type="aff" rid="aff4">4</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Brij .B Gupta</string-name>
          <email>gupta.brij@gmail.com</email>
          <xref ref-type="aff" rid="aff2">2</xref>
          <xref ref-type="aff" rid="aff3">3</xref>
          <xref ref-type="aff" rid="aff4">4</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Francesco COLACE</string-name>
          <email>fcolace@unisa.it</email>
          <xref ref-type="aff" rid="aff2">2</xref>
          <xref ref-type="aff" rid="aff4">4</xref>
          <xref ref-type="aff" rid="aff5">5</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Kwok Tai Chui</string-name>
          <email>jktchui@ouhk.edu.hk</email>
          <xref ref-type="aff" rid="aff1">1</xref>
          <xref ref-type="aff" rid="aff2">2</xref>
          <xref ref-type="aff" rid="aff4">4</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Department of Computer Engineering, National Institute of Technology Kurukshetra</institution>
          ,
          <country country="IN">India</country>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Hong Kong Metropolitan University (HKMU)</institution>
          ,
          <country country="HK">Hong Kong</country>
        </aff>
        <aff id="aff2">
          <label>2</label>
          <institution>IoV</institution>
          ,
          <addr-line>DDoS, IoT, Machine learning, SVM, J48</addr-line>
        </aff>
        <aff id="aff3">
          <label>3</label>
          <institution>National Institute of Technology Kurukshetra</institution>
          ,
          <addr-line>Kurukshetra, Haryana 136119</addr-line>
          ,
          <country country="IN">India</country>
          ,
          <institution>&amp; Asia University</institution>
        </aff>
        <aff id="aff4">
          <label>4</label>
          <institution>Taichung 413, Taiwan &amp; Staffordshire University</institution>
          ,
          <addr-line>Stoke-on-Trent ST4 2DE</addr-line>
          ,
          <country country="UK">UK</country>
        </aff>
        <aff id="aff5">
          <label>5</label>
          <institution>University of Salerno</institution>
          ,
          <country country="IT">Italy</country>
        </aff>
      </contrib-group>
      <abstract>
        <p>The concept of the Internet of Vehicles (IoV) enhances the VANETs by merging the VANETs with the Internet of things (IoT) thus making intelligent transportation systems a reality. The intelligent transport systems generate greater volumes of critical dynamic realtime data and thus raise a concern in the security of the generated data. The IoV has become a prominent field because of its scalability, reliable internet connection, and dynamic topological structures and due to its compatibility with various devices and sensors. IoV is susceptible to a range of attacks. The IoV consists of various kinds of components which involve various communications with sensors, vehicles, road infrastructure and humans. This paper will focus on UDP based Distributed Denial of Service (DDOS) Flood attacks. Onboard unit (OBU) is a computational device present in the vehicle is a resourceconstrained device a lightweight DDoS detection machine learning algorithm is required to detect the DDoS attack performed on the vehicles by a dataset generated using OMNET++ simulator.</p>
      </abstract>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>
        With the exponential increase of usage of vehicles and changing relationships among the vehicles,
their communications raise a concern in the security of their communication as they are prone to
become highly complex. IoT is described as connected smart devices that interact with the
environment surrounding them. Many advances of the IoT, are integrated into vehicles to model
Intelligent Transportation System (ITS). The IoV is a subset of IoT in which the data or the
information generated is shared among vehicles, pedestrians, infrastructures, and traffic lights. A
reliable and efficient communication service can be achieved by implementing the IoV [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ]. In order to
realize the concepts of smart cities ITS techniques have to be employed. The 5G enabled
communications has been employed to IoV to increase the bandwidth for the users thus resulting in
more amount of information being transmitted in the IoVs. Moreover, the network of the IoV is an
open network in which any user who might be an attacker can also join the network. The networks of
IoV are open because that the IoV networks are prone to attacks that are caused by the worm and the
Trojan horses and cyber-attacks [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ].
      </p>
      <p>There are 5 types of heterogeneous communication involved when the vehicle is communicating
with the surrounding objects they are of Vehicle-to-Vehicle (V2V), Vehicle-to-Roadside Units (V2R),
Vehicle-to-Personal devices (V2P), Vehicle-to-Sensors (V2S), and
Vehicle-to-Infrastructure of
networks (V2I) Fig. 1. The data or the information generated by the IoV is categorized into two:
on</p>
      <p>
        2020 Copyright for this paper by its authors.
road and onboard data. Vehicle's status like brakes, the velocity of the vehicle and working of various
components of the engine are monitored by onboard data. The functionalities that are carried out on
the road such as distance between the vehicles, pilot camera, blind spots and the traffic lights [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ] are
monitored by the on-road data. To perform the computations an onboard unit (OBU) is present within
the vehicle. It is also used to carry out Inter as well as intra communications that are depicted in
Figure 1.
      </p>
      <p>
        The Distributed Denial of Service (DDoS) [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ] attack is one of the major threats for vehicles
present in the IoV. Among the taxonomy of DDoS attacks flooding attacks are of major concern as
they exhaust the cache and the computing resources of the OBU present on the vehicles. DDoS attack
creates huge traffic using the DDoS attack from which the attacker exhausts the resources of the
targeted host like the network bandwidth and the CPU time[26].
      </p>
      <p>
        Some of the examples of DDoS attacks are DNS flood, SYN Flood, UDP flood and Ping Flood
[
        <xref ref-type="bibr" rid="ref5">5</xref>
        ][
        <xref ref-type="bibr" rid="ref6">6</xref>
        ]. The OBU of the vehicles is connected to various devices through wired and wireless means
where each and every component is connected globally.
      </p>
      <p>
        As the devices are connected globally and the resources of these devices have highly controlled the
security of IoV becomes highly challenging[
        <xref ref-type="bibr" rid="ref3">3</xref>
        ]. In our paper, we implement an anomaly-based
lightweight DDoS detection, we generated a dataset using the OMNET++[19], sumo[20] veins[22]
and INET[21] tools in order to generate a dataset for the UDP flood attack and for reducing the
number of features and an efficient feature selection algorithm Correlation-based feature selection
algorithm is used to train a machine-learning algorithm Support vector machine(SVM) and the J48
classifier to classify the incoming traffic as positive or negative. Many researchers have proved that
the SVM classifier has outperformed other classifier algorithms like k- nearest neighbour, random
forest and even neural networks [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ] in order to verify this claim we used the J48 classifier to compare
it with SVM.
      </p>
    </sec>
    <sec id="sec-2">
      <title>2. Related work</title>
      <p>
        Recently, authors propsed different techniques for DDoS attack detection [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ][13][
        <xref ref-type="bibr" rid="ref10">10</xref>
        ]. Authors of
[
        <xref ref-type="bibr" rid="ref9">9</xref>
        ] proposed an anomaly detection scheme for VANETs in which they have used a convolution neural
network for extracting the feature of the network traffic and to distinguish the incoming traffic they
have used a threshold-based separation method.
      </p>
      <p>This approach [11] is an anomaly-based DDoS detection approach that uses Cauchy distribution
based optimization for the feature selection and uses SVM based classifier for the attack
classification.</p>
      <p>The authors of [12] presented an intelligent transport system using visual analytics in order to
detect intrusions in road traffic data by integrating various data mining algorithms.</p>
      <p>The authors of this model [25] used the Correlation-based feature selection for reducing the
number of features to 7 and performed the classification using a machine learning algorithm called
J48 classifier on a Raspberry Pi and achieved satisfactory results for an IoT scenario.</p>
      <p>The support vector machine-based IDS proposed in [27] uses 3 features that are extracted from the
packet arrival rate. Performance evaluation of this approach is done on a MatLab simulation and
achieved satisfactory results for the DoS attack.</p>
      <p>In [28], in order to find out the anomalous nodes in the IoV network, the authors have proposed a
statistical approach IDS for analysing the traffic flows. The model analyses the traffic and based on
the insights provided by the model it classifies as an attack or not. The model can detect the
anomalous nodes and attacks in the network.</p>
    </sec>
    <sec id="sec-3">
      <title>3. Motivation</title>
      <p>The works proposed in the above approaches were designed using the datasets which were not
suitable for the IoV and VANET scenarios. So a dataset especially created for the DDoS for the IoV
scenario is much needed. Also, the works proposed earlier were focused on VANETs and hardly there
is research done in the field of IoV for detection of cyberattacks in IoV. These things were considered
in order to move ahead with our approach.</p>
    </sec>
    <sec id="sec-4">
      <title>4. Proposed approach and Implementation</title>
      <p>A dataset is needed in order to design an anomaly-based approach for the IoV and the dataset
should be related to the IoV scenarios. To get UDP based DDoS dataset we used simulators to
generate the data. This dataset will be used to train the machine learning model which is deployed in
the OBU of the vehicles. The tools which were used and their functionality are given in Table 1. A
realistic test bed is required in order to get a perfect dataset. The SUMO tool is used for generating
mobility traffic which is realistic. This traffic is imported into the OMNET++. The OMNET++ will
use the INET libraries and VEINS framework to generate the network traffic in which the normal and
attack packets for the IoV scenarios are configured. The resulting simulation generates scalar and
vector files that keep track of every instance that took place during the simulation. These result files
are filtered and labelled using the various SQL and normalizing techniques to obtain the required
dataset.</p>
      <p>Description
Amount of data for a given amount of time
Number of packets received from Higher layers
Number of packets received from Lower layers</p>
      <p>Count of the Packets</p>
      <p>The implementation flow of the proposed approach is given in Figure 2.</p>
      <p>The resulting dataset has 29 features with 90350 instances which make it a heavy anomaly model
for the OBU to process as it is power and resource-constrained. Hence it is necessary to make the
model lightweight. We used a correlation-based feature selection model [15] to select the features that
will be sufficient for training the model. In order to evaluate the performance of the dataset, we used
J48 [18] and SVM[14] classifier machine learning algorithms. In order to evaluate the performance of
the machine learning models, we used Raspberry Pi3b+ [23] which is a resource and
powerconstrained device like the OBU present in the vehicles. Brief information about the CFS and J48,
SVM classifiers is given below.
4.1.</p>
      <p>Correlation based feature selection
“The algorithm evaluates the relation between output and correlated inputs”[15]. The features for
a classifier machine learning model can be selected based on the correlation among the features. The
irrelevant and redundant features are ignored by this algorithm. The redundancy of a feature is
determined by the algorithm when it is correlated with one feature or more features. The subset of
features is selected when they are highly related to class and not correlated with each other. To
improve the accuracy and for reducing the computation of the machine learning model the features
that are redundant and not relevant are ignored. A subset of features with the highest merit is selected
as the feature set and the selected features are utilised in order to train the proposed model. The merit
of a feature subset is given by equation 1. In the equation the number of features present in a given
subset is defined by k, the average of feature-class correlation is given by rcf and the average of
feature-feature correlation is given by rff.</p>
      <p>=</p>
      <p>̅
√ + ( −1) ̅
(1)</p>
    </sec>
    <sec id="sec-5">
      <title>J48 Classifier</title>
      <p>It is a machine learning classifier algorithm proposed by Ross quinaln[18] and it is one of the
decision tree generation algorithms. The J48 classifier is also a statistical classifier. The structure of
the J48 classifier is a tree-like structure that has root nodes and leaf noodles which consists of the
attributes or classes. The main advantage of J48 is that it can handle both continuous and discrete
features. The overfitting problem in J48 can be solved by using the pruning techniques. The J48
classifier can also be used for datasets that do not have complete data in their datasets or even with
non-significant features.
4.3.</p>
    </sec>
    <sec id="sec-6">
      <title>Support vector machine(SVM)</title>
      <p>“The support vector machine (SVM) is a supervised machine learning algorithm which is used for
both classification and regression purposes”[14]. Wide ranges of applications use SVM as a classifier.
The working of SVM is based on the support vectors and hyperplane.</p>
      <p>A hyperplane is a flat subspace that has one less dimension of the coordinate system that it is
represented. For a 2-d coordinate system it is given by P0 + P1X1 + P2X2 = 0 In m-D coordinate it is
represented by P0 + P1X1 + P2X2 + …… + PmXm = 0.</p>
      <p>The CFS algorithm is applied to the dataset generated from the simulation with the help of the
weka [24] evaluation tool and the top 4 features from the resulting feature set were chosen to train the
machine learning algorithms. The machine learning models were trained and tested in the weka
evaluation tool using the generated dataset that is divided into two parts one consisting of 63245
training instances and the other consisting of 27105 testing instances. By using the CFS algorithm the
features are reduced to 4 and all the instances of the training data set were handled by the Raspberry
Pi and the dataset was used for evaluating the model on the WEKA tool by using the SVM and J48
classifiers.</p>
      <p>The performance parameters of the model with SVM and J48 are compared and observed which is
given in section 5. The parameters used for evaluating are the confusion matrix, F-measure, recall,
precision, “False positive rate (FPR), True positive rate (TPR), False Negative rate (TNR), True
Negative rate (TNR) and accuracy”.</p>
    </sec>
    <sec id="sec-7">
      <title>5. Results and observations</title>
    </sec>
    <sec id="sec-8">
      <title>5.1. Results</title>
      <p>The dataset generated by the OMNET++ simulator was fed into the CFS algorithms and the top
four features of the selected feature set by the CFS algorithm are given in the Table 2 along with their
description.performance parameters of the model with SVM and J48 are compared and observed
which is given in this section.
The confusion matrixes for the J48 and SVM classifier are given in Figure 3 and 4 respectively.</p>
      <p>A classified instance is said to be true positive if the classified instance is an attack packet. An
instance is said to be true negative if the classified instance is a normal packet. An instance is said to
be false positive if the instance is a normal packet but classified as attack packet. An instance is said
to be false negative if the instance is an attack packet but classified as normal packet.</p>
      <p>By using CFS we have achieved lightweight DDoS detection for OBU by greatly reducing the
number of features. It is known that if the number of features are more, the system becomes more
complex and it requires more computational power. By reducing the number of features from 29
to 4 we can observe that the complexity is greatly reduced and hence our system uses less power
and resources for computation.</p>
      <p>It can also be seen that the J48 classifier provided better detection accuracy when compared to
SVM as the false positive rate of the J48 is much lower than the false positive rate of SVM.
Hence we can say that J48 classifier can be used as the machine learning model to design the
anomaly-model for the IoV.</p>
    </sec>
    <sec id="sec-9">
      <title>6. Conclusion and future plan</title>
      <p>The IoV is an emerging technology and becoming a reality and due to its open network nature, it is
vulnerable to cyber-attacks. In this paper, we implemented a lightweight anomaly-based DDoS
detector to distinguish the network traffic from various devices to OBU in order to safeguard the
OBUs. To achieve this in a lightweight scenario CFS algorithm is used for reducing the feature from
the dataset we have generated using the OMNET++ simulator which has the instances for normal and
UDP based DDoS flood attacks. The features are reduced from 29 to 4; these four features are used to
train the machine learning Algorithms J48 and SVM on the test dataset. The models were evaluated
on the WEKA evaluation tool which is installed on Raspberry pi 3b+. The models were compared
according to their detection accuracy and it is evident that the J48 classifier outperformed the SVM
classifier and the CFS algorithm has made the system lightweight by reducing the number of features.
The applications for the proposed model can be further extended into various scenarios of the Internet
of Everything (IoE) such as healthcare, smart cities, Agriculture, Industries, and irrigation. For future
work, we can extend the instances in the dataset for various cyber-attacks which can be used to model
an intrusion detection system for the Internet of vehicles.
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