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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Real-Time Intrusion Detection via Machine Learning Approaches</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Erik Murtaj</string-name>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Fausto Marcantoni</string-name>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Michele Loreti</string-name>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Michela Quadrini</string-name>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Hans-Friedrich Witschel</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>FHNW University of Applied Sciences and Arts Northwestern Switzerland</institution>
          ,
          <addr-line>Riggenbachstrasse 16, CH-4600 Olten</addr-line>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>School of Science and Technology, University of Camerino</institution>
          ,
          <addr-line>Via Madonna delle Carceri, 9, Camerino, 62032</addr-line>
          ,
          <country country="IT">Italy</country>
        </aff>
      </contrib-group>
      <abstract>
        <p>In many cybersecurity contexts, the real-time detections of hostile actions play a fundamental role in protecting network infrastructures. In this scenario, Intrusion Detection Systems (IDS), based on signature-based or anomaly detection, are widely used to analyze network trafic. The signature-based detection relies on databases of known attack signatures, and anomaly detection is mainly based on Artificial Intelligence (AI) techniques. The latter is promising to detect new kinds of cyberattacks in real time. In this work, we propose ReTiNA-IDS, a framework that integrates the CICFlowmeter tool with Machine Learning techniques to analyze Real-Time network trafic patterns and detect abnormalities that may suggest a possible intrusion. The considered machine learning techniques, random forest and multi-layer network, are based on selected features to enhance eficiency and scalability. To select the features and train the models, we use a version of the public dataset, CSECICI-IDS2018. The framework's efectiveness has been tested in real-case scenarios by identifying diferent forms of intrusion. Analyzing the results, we conclude that the proposed solution shows valuable features.</p>
      </abstract>
      <kwd-group>
        <kwd>eol&gt;Random Forest</kwd>
        <kwd>Feature Selection</kwd>
        <kwd>analysis of Real-Time network trafic</kwd>
        <kwd>Intrusion Detection Systems</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
    </sec>
    <sec id="sec-2">
      <title>2. Related Works</title>
      <p>
        The use of machine learning approaches in intrusion
detection systems to obtain real-time analysis has been
exploited by many researchers. Many of them take
advantage of Deep Learning (DL) approaches. ARCADE is an
unsupervised DL-based approach for early anomaly
detection using 1D Convolutional Neural Networks (CNNs)
proposed by Lunardi et al. [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ]. The approach builds
a profile of normal trafic based on raw packet bytes.
      </p>
      <p>
        Kathareios et al. designed and tested a real-time
network AD system, able to operate on encrypted and non- 3.1. CICFlowMeter
encrypted network packets, based on two learning stages:
an autoencoder for adaptive unsupervised AD and a CICFlowmeter is a network trafic flow generator and
custom nearest-neighbour classifier to filter false pos- analyser [13, 14]. It generates bidirectional flows, where
itives [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ]. Shuai proposed a prototype that combines the first packet determines the forward (source to
destibig data processing frameworks like Apache Hadoop, nation) and backward (destination to source) directions.
Apache Kafka, and Apache Storm, along with ML tech- The tool enables the extraction of more than 80
statistiniques, i.e., Naïve Bayesian (NB), Support Vector Machine cal network trafic features such as Duration, Number of
(SVM), and Decision Tree (DT). The proposed approach packets, Number of bytes, Length of packets, etc. Such
considers six features related to the IP addresses of the features can be calculated independently for both
direcsender, receiver, and correspondent port without taking tions. The tool is developed in JAVA and provides a useful
into account flow measurements. Ho et al. suggested an Graphical User Interface, shown in Figure 1 to monitor
Intrusion Detection System (IDS) based on CNN that clas- network flows in real-time. TCP flows are usually
termisifies all packet trafic as benign or malicious, detecting nated upon connection teardown (by FINpacket), while
network intrusions [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ]. Atefnia and Ahmadi proposed a flow timeout terminates UDP flows [15].
a modular deep neural network model that consists of
four complete architectures that are combined with an
aggregator module, each generating distinct outputs [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ].
      </p>
      <p>
        The four architectures are a Deep Feed-Forward
Module (DFFM), a Stacked Restricted Boltzmann Machine
Module (SRBMM), and two recurrent modules, one
utilizing gated recurrent units (GRUM) and the other
utilizing long short-term memory (LSTMM). Catillo et al. [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ]
proposed an approach based on Deep Autoencoder, and
Fitni and Ramli [6] proposed a model based on
decision trees that takes into account 23 features selected
by Spearman’s rank correlation coeficient [ 7]. Gamage
and Samarabandu considered four DL architectures, i.e.,
feed-forward neural network, autoencoder, deep belief
network, and LSTM [8]. Karatas et al. in [9] reviewed Figure 1: Example of the CICFlowmeter’s GUI
the implementation of a Synthetic Minority
Oversampling Technique (SMOTE) [10] to balance the data by The tool is developed in JAVA and provides a useful
exploiting six models. Kanimozhi and Jacob presented GUI (Graphical User Interface) to monitor network flows
a two-layer MLP to detect only botnet attacks that ex- in real time.
ploit a grid search for hyper-parameter optimization and
a 10-fold cross-validation for mitigating the overfitting 3.2. Machine Learning Approaches and
problems [11]. Huancayo Ramos et al. extended this
approach by considering botnet data and Random Forests. Feature Selection
Kim et al. also designed a model that exploits CNN for
training on a single type of attack, specifically Denial of
Service (DoS) attacks [12].
      </p>
    </sec>
    <sec id="sec-3">
      <title>3. Background</title>
      <p>In this section, we present the CICFlowMeter, an
Ethernet trafic Bi-flow generator and analyzer for anomaly
detection, and the Random Forest, a machine learning
method used for classifying flow data and evaluating
the importance of features. This classifier will then be
integrated into CICFlowMeter for classifying network
lfows.</p>
      <p>The Random Forest is an ML ensemble model used for
both classification and regression tasks. During training,
the model creates numerous decision trees and
determines the output class by either the mode (for
classification) or the mean/average prediction (for regression)
of the classes predicted by individual trees. Introduced
by Breiman in [16], this approach combines the bagging
technique with the random selection of features. Such a
random selection ensures that the decision trees within
the forest are uncorrelated. In the bagging phase,
decision trees are constructed from bootstrap samples of
the training dataset, where each sample is drawn with
replacement, allowing for the possibility of repeated
samples. These replicated datasets are then used to train
decision trees, ensuring that each tree only sees diferent
portions of the original dataset during training. This
bagging approach is coupled with random feature selection,
which involves using distinct random subsets of the en- Table 2
tire feature space to train each tree in the random forest. The first 13 attributes ordered by importance
Usually, around √ features are employed in each split Id Attribute
for a classification task that considers ′′ features. 1 FWD Init Win Bytes</p>
      <sec id="sec-3-1">
        <title>3.3. Dataset: CSE-CIC-IDS2018</title>
        <p>The data used in this study is the CSE-CIC-IDS2018, a
benchmark dataset for the evaluation of IDSs. Such data
was collected by the Communications Security
Establishment (CSE) and the Canadian Institute for Cybersecurity
(CIC). The recorded data consists of ten days of trafic
and includes seven types of attacks. Liu et al. identified
some issues in such dataset related to the creation
lifecycle, including attack orchestration, feature generation,
documentation, and labelling and provided to reconstruct
the datasets by deleting artefacts and corrected labelling
logic, including corrected implementations of existing
features and new features that capture valuable flow state
information [17]. Table 1 reports the corrupt amount of
data.</p>
        <sec id="sec-3-1-1">
          <title>Attack Type</title>
          <p>Bot
Web - Brute Force
Web Attack - XSS
DoS Attacks
DDoS Attacks
FTP-Patator
Infiltration
SQL Injection
SSH-Patator
Corruption Rate (%)</p>
        </sec>
      </sec>
      <sec id="sec-3-2">
        <title>3.4. Metrics</title>
        <p>We evaluate the performance and efectiveness of the
approaches by using Precision ( ), Recall () and , defined
as follows
 =
 =</p>
      </sec>
    </sec>
    <sec id="sec-4">
      <title>4. ReTiNA-IDS Approach</title>
      <p>ReTiNA-IDS, Real-Time anomaly Detection IDS
Approach, integrates a ML model mainly based on
Random Forest in the CICFlowMeter tool to detect
Real-Time cyber-attacks and act as a simple IDS. The
Random Forest classifier considers only 13 of the 80
features calculated by the CICFlowMeter tool. The list
of features with the relative description, selected by
another Random Forest model, is in Table 2. After being
trained, the model has been exported in a pmml format
with the use of the “sklearn-pmml-model“ library from
Sklearn [18]. The exported model is then imported into
CICFlowMeter, which is developed in Java.</p>
      <sec id="sec-4-1">
        <title>4.1. ML Pipeline</title>
        <p>The proposed approach is based on Random Forest,
described in Section 3.2, and its scheme is shown in Figure 2.
In this study, the used dataset is a revised version of
CSE-CIC-IDS2018, as introduced in Section 3.3. The
dataset consists of the network trafic captured on ten
days, stored in 10 distinct files according to the day of
data capture, as shown in Table 3.</p>
        <p>The first step of the preprocessing consists of data
cleaning, i.e., removing missing values, such as
incomplete rows, and containing invalid (or infinite) numerical
values. Moreover, many non-relevant features for
spotting cyber-attacks have been eliminated, such as the IP
address of the sender and receiver, the connection
timestamp, the protocol type, and the destination/sender port.
Furthermore, the trafic data related to Web Attacks is
deleted since its volume is insuficient.</p>
        <sec id="sec-4-1-1">
          <title>4.1.2. Data Balancing and Data Augmentation</title>
          <p>Class
BENIGN
DoS Attack
BruteForce Attack
PortScan Attack
BotNet Attack
Total</p>
          <p>The collected data related to network trafic is
substantially unbalanced: benign trafic is more prevalent than
malicious trafic. To balance the data, we have used the
one step of the bootstrapping procedure, implemented
in the resample function of Sklearn. Due to the corrupted
data on the original dataset, it does not contain data
related to FTP Brute Force attacks. Therefore, we have
added this kind of data by collecting such data during a Figure 3: Confusion Matrix of the Random Forest Classifier
simulation of brute force attacks via FTP (File Transfer
Protocol). The simulation involved the use of a Windows The performance of the model, evaluated in terms of
host (victim machine) and a Kali-Linux host (attacker ma- Precision, Recall and 1-score, is shown in the Table 5.
chine), both in the same local area network (connected
to the same router). The victim machine runs a FileZilla
server, an open-source software utility that facilitates the 5. Experimental Setup
transmission of files using the File FTP. It enables users
to establish their own FTP servers or connect to existing
FTP servers to exchange data, and the victim machine
accepts connections on port 21, used to attack. When the
FileZilla server on the victim machine is running, the Kali
Linux host performs a brute-force attack using Patator, a
multi-purpose brute-forcer tool [19]. Table 4 shows the
amount of data and the relative kind of attack, after the
cleaning and balancing phases.</p>
          <p>The ML models have been implemented in a Google
Colab document with Python 3. The default CPU in the
environment is an Intel Xeon CPU equipped with 2
virtual CPUs (vCPUs) and 13GB of RAM [20]. For this study,
the configuration involved the utilization of extra RAM,
resulting in a total memory capacity of 50GB (included
with Google Colab Pro [20]).</p>
          <p>For data handling, preprocessing, analysis, training,
and evaluation metrics, the recommended model was
built and evaluated using Numpy [21], Pandas [22], and
4.1.3. Feature Selection and Classifier Scikit Learn [23]. Matplotlib [24] were used to
visualTo select the features, a Random Forest has been consid- ize the data. The testing phase for this study used a
ered and implemented by setting up the depth of each Windows operating system for the with the following
decision tree and number of estimators to 16 and 20, specifications: an Intel Core i5-4670 CPU at 3.40GHz, 16
GB of DDR4 memory and a Nvidia GTX 1050 Ti GPU.</p>
        </sec>
      </sec>
      <sec id="sec-4-2">
        <title>5.1. Testing</title>
      </sec>
    </sec>
    <sec id="sec-5">
      <title>6. Conclusion and Future Work</title>
      <p>Retina-IDS, a tool that integrates an ML model into CI- In this work, we have presented ReTiNA-IDS, a tool that
CFlowMeter, analyzes data patterns and distinguishes integrates an ML model into CICFlowMeter, which
anabenign trafic from malicious trafic. The testing phase of lyzes data patterns and distinguishes benign trafic from
ReTiNA-IDS intends to assess the eficiency and eficacy malicious trafic in real-time. The ML model is based on
of the machine learning model in real-world network a Random Forest, used to select features and to classify
situations. We take advantage of the Graphical Network the data. The testing phase, performed by running the
Simulator-3 (GNS3) software, an open-source network tool in a normal trafic situation (without performing
simulation tool used for creating, modelling, and testing any cyberattack) in a local network and the University
virtual and real networks [25], to perform the simulations. of Camerino’s network, shows that the tool does not
To reach the aim, we create a simple network composed identify false positives.
of a Cisco router [26] and two generic switches, outlining In the near future, we intend to test the approach in
bottwo diferent areas of a hypothetical Local Area Network net trafic to investigate the performance of the
ReTiNA(LAN), a Windows machine and a Kali Linux machine. IDS. To reach this aim, we intend to create a central server
Figure 4shows the network infrastructure. to control potentially infected hosts. Moreover, we have
planned to consider other machine learning models, both
supervised and unsupervised. Moreover, motivated by
the results obtained for modelling and verifying
properties of Collective Adaptive Systems [27, 28, 29], we
intend to define formal approaches to specify and verify
properties of the data trafic to monitor the trafic and
identify anomalous pattern in the trafic.</p>
      <p>The Windows machine represents the hypothetical
victim running the Retina-IDS tool, acting as an IDS,
while the Kali Linux machine plays the role of attacker.</p>
      <p>The victim machine is a Windows 10 host, while the
used Kali Linux version is Kali 2023.4. Instead, the victim
machine is a Windows 10 host.</p>
      <p>Diferent attack simulations were performed, each one
resulting in a positive detection by the tool:
• DoS attacks
• File Transfer Protocol (FTP) and Secure SHell</p>
      <p>(SHH) Bruteforce attacks
• Portscan attacks</p>
      <p>Additionally, more tests were performed with the tool
running in a normal trafic situation (without performing
any cyberattack) in a local network and in the University
of Camerino’s network, for a total of around 5 hours of
workload. The purpose of letting the tool run for hours
on end was to see whether any crashes occurred during
execution and to spot any false positive results. During
the experiments zero false positives were identified.</p>
      <p>Acknowledgements. This work has been funded by
the European Union - NextGenerationEU under the
Italian Ministry of University and Research (MUR) National
Innovation Ecosystem grant ECS00000041 - VITALITY
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