=Paper=
{{Paper
|id=Vol-2608/paper69
|storemode=property
|title=Development of a network attack detection system based on hybrid neuro-fuzzy algorithms
|pdfUrl=https://ceur-ws.org/Vol-2608/paper69.pdf
|volume=Vol-2608
|authors=Olexander Belej,Liubov Halkiv
|dblpUrl=https://dblp.org/rec/conf/cmis/BelejH20
}}
==Development of a network attack detection system based on hybrid neuro-fuzzy algorithms==
Development of a Network Attack Detection System
Based on Hybrid Neuro-Fuzzy Algorithms
Olexander Belej1 [0000-0003-4150-7425], Lіubov Нalkiv 2 [0000-0001-5166-8674]
1
Lviv Polytechnic National University, 5 Mytropolyt Andrei str., Building 4, Room 324, Lviv
79013, Ukraine
Oleksandr.I.Belei@lpnu.ua
2
Lviv Polytechnic National University, 12, Stepan Bandera str, 79013, Lviv, Ukraine
Lubov.I.Halkiv@lpnu.ua
Abstract. The imperfection of existing intrusion detection methods, as well as
the changing nature of malicious actions by the attacker, make computer sys-
tems unsafe, therefore it is important to identify new types of attacks and re-
spond to them on time. The developed hybrid scheme for detecting and classify-
ing network attacks based on a combination of adaptive classifiers. The study
proposed a generalized scheme for combining classifiers to detect network at-
tacks. Based on it, a software tool has been developed that allows you to ana-
lyze network traffic for the presence of abnormal network activity. To reduce
the number of features used, it is proposed to use the method of principal com-
ponents. The main feature of the proposed approach is a multilevel analysis of
network traffic, as well as the use of various adaptive modules in the attack de-
tection process. Computational experiments were carried out on two open data
sets using various methods of combining classifiers. The developed modules
can be used to process data received from sensors of the information and secu-
rity events management system.
Keywords: network attack, intrusion detection system, algorithm, signal, traf-
fic, protocol, transmission.
1 Introduction
The detection of network attacks is one of the urgent problems of information security
due to the rapid development of computer technology and the imperfection of existing
methods for detecting attacks. To correct the situation in this area, the current efforts
of researchers are aimed at finding and applying new, including hybrid and adaptive,
detection schemes.
An intrusion detection system (IDS) is an important component of computer net-
work protection. Its main task is to monitor the network or system for malicious activ-
ity. Although the problem of detecting network attacks is quite old, it is still relevant.
Copyright © 2020 for this paper by its authors. Use permitted under Creative
Commons License Attribution 4.0 International (CC BY 4.0).
A few years ago, network intrusions were rare because they required extensive
knowledge of operating systems, network protocols. Today, any user can carry out
malicious actions on the network by downloading one of the exploit programs avail-
able on the Internet.
One of the most popular areas of development of computer security systems today
is the technology of artificial immune systems [1]. It is assumed that the use of meth-
ods and techniques for protecting the body from germs and viruses will overcome the
problems of classical means of ensuring information security.
In this paper, an attempt is made to create an intrusion detection system based on
the immune model. Based on the architecture of the IDS developed by Kim and Bent-
ley, which is called the immune model of intrusion detection [2]. Among others, it
most closely mimics the behavior of a biological immune system. However, accord-
ing to the authors of this article, some properties of immunity are absent in the Kim
and Bentley model, which negatively affects its effectiveness.
The detection of network attacks is one of the urgent problems of information se-
curity due to the rapid development of computer technology and the imperfection of
existing methods for detecting attacks. To correct the situation in this area, the current
efforts of researchers are aimed at finding and applying new, including hybrid and
adaptive, detection schemes.
Formal problem statement
In this study, an attempt is made to identify network attacks based on the analysis
of connections characterizing the activity of remote hosts. In this case, monitoring
network activity usually consists of the following steps. At the first stage, the filtering
of incoming and outgoing packets collected with the help of sensor agents installed by
controlled network nodes is performed. At this stage, packet aggregation also takes
place to form signs of an established session concerning a unique pair of sockets. At
the next stage, the data collected from the first level is stored in a repository for their
subsequent processing and interpretation. At the last stage, the administrator is noti-
fied of the detected changes in the security policy and offers possible solutions to
prevent the further development of the invasion.
Network IDSs are based on the analysis of network traffic that passes through the
sensors and, in the event of anomalies, is sent to the analyzers for further decision
making. In large information systems (IS), the problem of a large amount of network
traffic arises, since standard approaches to data processing are no longer effective. To
increase the efficiency of identifying situations associated with a possible intrusion,
recently, modern technologies of data mining have been widely used. One of the most
effective approaches to classifying a large amount of data is the use of neural net-
works. This method allows you to detect not only already known network attacks, but
also to identify new ones.
The main task of processing network data lies with the intrusion detection subsys-
tem, which is responsible for analyzing network traffic. The effectiveness of IDS
directly depends on the chosen method of constructing an algorithm for detecting
attacks and processing a large amount of network data. The aim of this work is to
develop an intrusion detection algorithm by processing and filtering a large amount of
network traffic, based on an artificial neural network.
2 Literature review
Currently, many works investigate the applicability of the methods in question to
detect attacks. We will present some of these works in more detail. As a training set
for artificial neural networks, various data can serve. So, in [3, 4], to solve this prob-
lem, it is proposed to use a multilayer neural network trained on data from a variety of
Snort signatures. In works [5, 6] many KDD Cup records are used as training data.
Modeled connections are another source of data. An example of a work in which
the author used a three-layer direct distribution neural network as a binary classifier of
network connections is an article [7]. These works are united by the general idea of
using one classifier aimed at identifying illegitimate traffic.
Other authors [8, 9] propose a model of the immune system with the life cycle of
T-lymphocytes, which took into account the process of their maturation in the thy-
mus, as well as activation, the formation of immune memory cells through a stimula-
tion signal and the death of immune cells. The lightweight immune system (LISYS)
developed is designed to detect intrusions in a distributed environment. Although this
system has several advantages, including relatively low computational overhead, reli-
ability, and scalability, the authors note some of the disadvantages. The inability to
detect network attacks using the UDP protocol and the ability to trick the system by
conducting distributed attacks over time such as slow-scanning [10]. It provides an
overview of a two-level intrusion detection system, which combines the advantages of
Kohonen's immune systems and networks. At the first stage, the signs of network
connections are filtered using immune detectors trained by the negative selection
method, thereby eliminating those samples that correspond to normal connections. In
the second stage, abnormal instances are processed by self-organizing cards and
grouped into separate clusters with similar features. It also presented a two-level
model in which immune systems were used to detect anomalies, and neural networks
with the principal component method were used to detect abnormalities [11].
The application of neuro-fuzzy systems to intrusion detection problems was dis-
cussed in [12]. Their authors used the parameters of the KDD Cup 99 and DARPA
1998 datasets as input for fuzzy classifiers based on the fuzzy inference.
There are also various hybrid approaches, for example, a combination of the appa-
ratus of immune systems and neural networks [13]. Multilayer neural networks that
are generated using the clonal selection method are selected as immune detectors. The
experiments were carried out on the KDD Cup 99 dataset; they proved the high ability
of the detectors to adapt to new types of attacks.
Another hybrid solution to intrusion detection is to combine several neural net-
works into a single classifier. So, work [14] is devoted to the application of the IDS
method and radial basis networks for the classification of records from the NSL-KDD
data set. The final classifier is presented as a composition of classifiers sequentially
built on different samples and simple voting procedures. As a result, the classification
level was increased by about 1.6% compared with the classifiers taken separately.
Other authors [15] propose submitting output values from several neural networks
trained by various algorithms to the input of the weighted voting and majority voting.
On a test sample of 6890 samples, a classification accuracy of over 99% was
achieved.
Article [16] describes a two-level scheme for detecting and classifying attacks.
Several adaptive neuron-fuzzy modules are combined. Each of them is designed to
detect only one class of compounds, processes the parameters of the KDD Cup 99
records. The final classification is performed by the fuzzy decision module, which
implements the neuro-fuzzy inference system with two membership functions. This
module is responsible for determining how abnormal the record being processed is. Its
class corresponds to the class of the fuzzy module of the first level with the highest
output value.
Previous work [17, 18, 19] has focused more on the transmission of chaotic signals
using dynamic models. The offered algorithm of transfer images can be used for the
decision of control tasks for integrity data and transfer of the information in modern
telecommunication and information systems [17]. In the article [18] considered an
algorithm of constructing an electronic-digital message signature based on encryption
using elliptic curves. The article [19] is devoted to the calculation of the characteris-
tics of dynamic chaos based on the traffic of the corporate computer network.
This article proposes an approach that develops the considered work. It is based on
the implementation of multi-level and adaptive detection of network attacks through a
combination of neural networks. Adaptive detectors perform parallel processing of
input features of connections. The detectors are trained on various data samples and
are designed to classify a single compound.
3 Hybrid signature model and adaptive approach
The proposed hybridization scheme for signature and adaptive approaches is pre-
sented in Fig. 1. To analyze packets and generate session parameters, the IDS system
was used additional scripts were added for processing network events. The system has
a built-in script interpreter that provides processing of various network events.
Fig. 1. Hybrid signature model and adaptive approach.
When creating a record about each formed connection, the parameters necessary for
the classification of compounds are selected and calculated from the data field and
header of each packet. Statistics are also collected on currently open connections.
Optionally, to reduce the dimension, the input vector is compressed by the principal
component method. Each group of detectors trained to recognize one particular type
of connection processes the last set of features. The final classification result is issued
by the terminal classifier.
Within this scheme, several attack detection techniques can be used. The first of
them implies that each group consists of several classifiers of the same type, which
are trained on different samples from the training set. This allows you to create detec-
tors that differ from each other in adjusted weights, and thereby increase the quantita-
tive indicators of attack detection. The second technique involves the use of heteroge-
neous classifiers within each group. Here, instances of each of the three models are
used to recognize a specific type of attack. In both cases, the output values from all
classifiers can be considered as an input vector for the terminal classifier.
Let’s take a closer look at the attack detection process. It can be divided into three
stages.
At the first stage, the IP-defragmentation of raw packets and the assembly of TCP
session segments are performed. Each connection (session) is a sequence of TCP
packets for a certain time interval, during which data is transferred between a pair of
remote hosts and using a specific protocol.
In the process of analyzing network traffic, packets that initiate the start of a session
(SYN) and serve as a sign of its termination (FIN, RST, timeout) are monitored. Each
session can be characterized as a set of parameters, the elements of which are condi-
tionally divided into two groups: attributes obtained from the packet headers, and
statistical data. Also, this stage is responsible for the initial detection of network
anomalies by verifying that the contents of individual packets match the specified
regular expressions in the signature set.
The second step involves applying the principal component method and converting
the output parameters of each session into a compressed set of attributes. Each ele-
ment of the new vector is a linear combination of the elements of the old vector with
coefficients, which are elements of the eigenvectors of the covariance matrix of the
source data.
The third stage is the application of several groups of adaptive classifiers. Each
group consists of detectors responsible for recognizing one particular type of connec-
tion. To increase the classification rate, each detector processes an incoming set of
parameters in parallel with the others.
A terminal classifier can be represented in several ways. The simplest of them is
the majority voting procedure. In this case, the connection class is the one for which a
larger number of detectors within a certain group voted. Another method for imple-
menting the terminal classifier is a weighted vote and its modification. In this case,
each classifier will be assigned an appropriate coefficient assigned to it in the learning
process. This will allow more reasonable use of one or another classifier, depending
on its indicators of the correctness of recognition of attacks calculated on the samples
of the training set. The next approach is to choose the best classifier for each particu-
lar record and ignore the rest. The main difficulty here is the construction for each
classifier of a given area of competence in the space of attributes. It is also proposed
to use output values from first-level classifiers as a training set for a terminal classi-
fier. This technique, known as a multi-tiered generalization, can be built based on data
mining methods.
To achieve the goal, it is proposed to use three artificial neural networks (ANNs)
with various topologies: a multilayer perceptron (MLP), a network of radial basis
functions (RBF) and a self-organizing Kohonen map (SOM). The same traffic is sent
to the input of each ANN for the analysis of IP packet headers together with an inac-
curate search for intrusion signatures directly in the applied contents of IP packets. To
train an ANN, it is necessary to use both packets containing known signatures and
normal IP datagrams [8]. In the process of detection, each ANN determines how
much the network packet submitted to the input corresponds to a normal or abnormal
situation.
At the output of each ANN, the results are presented as a multidimensional vector,
each coordinate of which corresponds to one of the types of attacks. If the ANN de-
tects an attack, then the corresponding coordinate takes a single value, otherwise, it
takes zero.
The use of three ANNs with different topologies necessitates the conversion of
network traffic to a single format so that each of them can equally analyze the data
supplied to it at the input. The most suitable format is NLS-KDD, which is a standard
dataset for IDS. The NLS-KDD dataset contains raw network packets that are inde-
pendent of the operating systems used. In total, this data set includes 4898431 sam-
ples. NLS-KDD includes 37 different network attacks that can be divided into four
large groups: denial of service, privilege escalation, remote access, and network scan-
ning. All types of network attacks are presented in Table 1.
Table 1. Types of network attacks from the NLS-KDD dataset
Group of attacks Attacks
Denial of service Back, Land, Neptune, Pod, Smurf, Teardrop, Mailbomb, Processtable,
Udpstorm, Apache2, Worm
Network scan Satan, IPsweep, Nmap, Portsweep, Mscan
Getting Remote Guess_password, Ftp_write, Imap, Phf, Multihop, WarezmasterXlock,
Access Xsnoop, Snmpguess, Snmpgetattack, Httptunnel, Sendmail, Named
Privilege escala- Buffer_overflow, Loadmodule Rootkit, Perl, Sqlattack, Xterm, Ps
tion
The NLS-KDD format contains 41 fields. Bringing IP packets to NLS_KDD con-
sists of extracting some features from network traffic. Such signs include connection
duration, connection protocol, connection type, service and destination port, success-
ful connection flag, number of failed authorization attempts, number of connection
requests with administrator rights. The process of converting network packets to the
NLS-KDD format is shown in Fig. 2.
Upon completion of converting network data to a single NLS-KDD format, they
are fed to the input of the ANN. After analyzing the next portion of network traffic,
the results of the ANN are recorded in multidimensional vectors. The resulting vector
is found as the sum of the output vectors of the three ANNs. If the coordinate is zero
or one in the resulting vector, then there is no attack. A unit means that a false
positive occurred on one of the ANNs. If the value of the vector coordinate is 2 or 3,
then an attack of the corresponding type has occurred. In Fig. 3, the process of
obtaining the resulting vector is simplified.
Fig. 2. The process of converting network packets to the NLS-KDD format for further submis-
sion to the input of the ANN of various topologies.
Fig. 3. Simplified representation of the addition of resulting vectors.
Thus, the algorithm of IDS (Fig. 4), which processes and filters a large amount of
network traffic based on the ANN, will consist of the following: receiving suspicious
network traffic from the sensor subsystem; converting network packets to the NLS-
KDD format; analysis of a portion of n network packets using three neural networks
with different topologies of MLP, SVM, and SOM; analysis results are entered into
multi-dimensional vectors; the resulting vector is obtained by adding the three output
vectors MLP, SVM, and SOV. After that, it is transferred to the data presentation
subsystem.
Fig. 4. Algorithm for detecting network attacks using three ANNs with different topologies.
The capabilities of the proposed algorithm can be expanded both by increasing the
number of ANNs used and by using other types of ANNs depending on the task.
4 Experiments and results
To test the described models, two open data sets were selected: KDD Cup 99 and
NSL-KDD. For these sets, each record represents an image of a real network session,
described as a set of 41 parameters, and is marked as an attack or normal connection.
The developed intrusion detection system monitors the level of data obtained from
packet headers and statistical information generated by the sliding window method.
Therefore, 29 parameters were selected that satisfy this requirement. Also, for the
classification of connections, 5 types of DDoS attacks and 4 types of attacks such as
port scans were selected. The data received from the Bro system is processed by
modules that implement a mechanism for classifying compounds using the proposed
detectors. The following numerical indicators were selected to test the effectiveness
of the functioning of the models:
1. Percentage of samples of normal compounds recognized as attacks (false positive):
nFP
FP 100% . (1)
nFP nTN
2. The percentage of correctly recognized samples of abnormal compounds (true
positive):
nTP
TP 100% . (2)
nTP n FN
3. The percentage of network connection patterns whose class was correct classifica-
tion:
nCC
CC 100%
n . (3)
The threshold value for immune detectors was chosen experimentally in such a way
that
TP F CC max (4)
was fulfilled on the training data.
The experimental results for each approach with the indicated values of these pa-
rameters, which were used as the terminal classifier by the majority voting procedure,
are presented in Table 2.
Table 2. Indicators FP, TP, CC
An approach KDD Cup 99 NSL-KDD
FP TP CC FP TP CC
Neural networks 3,56 98,95 73,56 7,08 98,24 56,86
Immune detectors 2,26 91,16 94,82 12,51 93,06 65,65
Neuro-fuzzy classifiers 11,65 98,29 88,89 16,94 96,37 83,06
Combination of approaches 1,31 99,98 77,04 5,11 99,85 57,96
As can be seen from the results obtained, neural network and neuron-fuzzy classi-
fiers, in comparison with immune detectors, have a greater number of correctly rec-
ognized compounds when analyzing network parameters. So these classifiers are a
more preferable tool for detecting network attacks. At the same time, immune detec-
tors due to the dynamic configuration of the balance can modify their structure in
response to detected attacks. Therefore, in the process of analyzing network traffic,
the performance of recognition of network attacks by immune detectors increases
over time. This evolutionary mechanism, as well as an updated set of training data,
contributes to the recognition of previously unknown types of attacks.
Among the proposed three models, neural networks showed the best degree of rec-
ognition of network connection patterns. Neuron-fuzzy classifiers are characterized
by a long learning process. This is explained by the complexity of the calculations
associated with the multi-level structure of the network, and the setting of the parame-
ters of membership functions in fuzzy rules. Nevertheless, the attack detection rate for
these classifiers is high and comparable to the indicator of neural networks.
To evaluate the effectiveness of the proposed intrusion detection approaches, a se-
ries of experiments was conducted. The KDD Sup 99 database was used to train and
test neural network models. This is one of those few intrusion detection bases that has
attracted the attention of researchers due to its well-designed structure and accessibil-
ity. To study the characteristics of the proposed systems, we set three main indicators:
the share of detected, the share of recognized attacks for each class and the number of
false positives of the system. The share of detected attacks is defined as the number of
attack images of a particular class detected by the system divided by the total number
of records of attacks of this class in the database. Similarly, the share of recognized is
determined. False positives indicate the total number of images of normal network
operations that are erroneously classified as attacks.
The results of testing the recognition of an attack class for the operation of an
intrusion detection system for sensor wireless networks are shown in Table 3.
Table 3. Model 1 test results for intrusion detection
Class Total Discovered Recognized
DoS 391458 391441 (99.99%) 370741 (94.71%)
U2R 52 48 (92.31%) 42 (80.77%)
R2L 1126 1113 (98.85%) 658 (58.44%)
Probe 4107 4094 (99.68%) 4081 (99.37%)
Normal condition
Normal 97277 --- 50831 (52.25%)
Thus, the best result was achieved for DoS and Probe attacks. U2R and R2L are
determined slightly worse, respectively, 80.77% and 58.44%. Also, there is a percent-
age of false positives for the system. A summary of each of the options for building
an attack detection system is shown in Table 4.
Thus, model 3 is characterized by high accuracy (93.21%) and the least number of
false positives. Using model 1, 86.3% of the input images were recognized, and
model 2, 92.97%. Models 2 and 3 can be successfully used to work with large sets of
complex data structures.
Table 4. Test results of proposed intrusion detection models in intrusion detection systems for
sensor wireless networks
Model Detected attacks Recognized At- False positives Total share recog-
tacks nized, %
Model 396696 375522 (94,65%) 46446 86.30%
1 (99.98%) (47.75%)
Model 395949 375391 (94.61%) 13398 92.97%
2 (99.80%) (13.77%)
Model 396549 375730 (94.70%) 12549 93.21%
3 (99.95%) (12.90%)
Also, for each type of attack, the detection rates of various detectors were calcu-
lated. So, Table 5 shows indicators of the effectiveness of recognition of attacks on a
set of KDD Cup 99 combined classifiers. In the presented table, the left column is the
type of connection, the top row is the type of classifiers, their intersection is the per-
centage of correctly recognized attacks.
Table 5. Attack recognition performance indicators with combined classifiers for sensor
wireless networks, %
back neptune pod smurf teardrop ipsweep nmap ports- satan
p
back 100 0 0 0 0 0 0 0,46 3,37
neptune 0 99,98 0 0 0 0 0,56 99,99 99,93
pod 0 0 60,98 0 34,09 1,89 1,89 100 37,88
smurf 0 0 0 99,92 0 0 0,05 0 0,09
teardrop 0 0 56,63 0 100 0,2 0 100 100
ipsweep 0 0 0,4 0 0 100 91,95 1,69 0,4
nmap 0 0 0,43 0 0 44,16 100 44,59 44,59
ports-p 0,1 3,09 0,1 0 0 67,6 0,39 100 89,68
satan 0 88,64 0 0 0 9,28 0,25 88,26 99,87
normal 0,06 0,03 0,05 0,03 0 0,1 0,44 0,25 0,56
By combining individual classifiers, it was possible to increase the detection rates
by 3.85 and 3.96% compared with the average value of this value for individual clas-
sifiers for KDD Cup 99 and NSL-KDD, respectively. At the same time, the indicator
of correct classification remained above this indicator for neural networks.
The constructed intrusion detection system can be used in real computer networks
after preliminary training on the traffic characteristic of this network. In particular, at
present, the study is aimed at conducting experiments related to the newly generated
data. For this purpose, a software stand was created to simulate the computer network
of a large enterprise used for experiments with the developed SIEM system, taking
into account various vulnerabilities in software and hardware.
5 Conclusion
An implementation of a hybrid intrusion detection system, designed to analyze traffic
in computer networks using the TCP/IP protocol stack, is presented. One of their ad-
vantages is the flexible extensibility of functionality by writing additional scripts for
processing network events. This allows you to embed the necessary scripts designed
to generate session parameters. To analyze such parameters, three modules are pro-
posed that are based on various adaptive models: neural networks, immune detectors,
and neuron-fuzzy classifiers. The experiments were conducted on two data sets: KDD
Cup NSL-KDD. The results showed that, in comparison with the existing detection
approaches evaluated on these sets, the proposed integration scheme allows a com-
promise between the recognition of unknown types of threats and false positives.
As we noted above, there are a lot of ways to detect an intrusion into the system
and no fewer ways to hide it. We examined only one of them and proposed their
mechanism for detecting network attacks. Today, hackers are becoming smarter, so
you need to do a dump of RAM and its analysis. After that, we do a selective analysis
of the files on the hard drive. And only at the end - a full analysis of the hard disk, if
necessary.
Further research will focus on finding and applying other hybrid approaches to de-
tecting attacks, creating experimental data sets and conducting experiments.
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