Anomaly detection: An overview of selected methods

Malware authors are continuously developing crime toolkits. This has led to the situation of zero-day attacks, where malware harm computer systems despite the protection from existing Intrusion Detection Systems (IDSs). We propose an Intelligent Intrusion Detection and Prevention System (IIDPS) approach that combines the Signature based Intrusion Detection system (SIDS), Anomaly based Intrusion Detection System (AIDS) and Response Intrusion Detection System (RIDS). We used a risk assessment approach to determine an appropriate response action against each attack event. We also demonstrated the IIDPS make the detection and prevention of malware more effective.

The problem of the network security is taken up since eighties (Denning et al., 1987) and is developed up today (Beltilch et al., 2004, Bera, 2010, Dasgupta, 1999, Basile, 2007, Wilson, 1999). A major problem of automatic intrusion detection is that, it is difficult to make a difference between normal and abnormal user behaviour. Intrusion detection system should not only recognise the previously known patterns of attacks, but also react in case of appearance of the new events that violate the network security policy. The distributed nature of the task of the network security monitoring requires applying of the distributed tools for network security maintaining. The most important postulate addressed to the intrusion detection systems is that, such systems should automatically react in case of detecting the security policy breach to prevent the attack execution or to reduce the potential loss in the network systems. Intrusion detection systems should be equipped with the components responsible for the permanent observation of the states of monitored nodes and components that integrate the results of these observations and diagnose the security level of the system (Kolaczek et al., 2005, Nguyen et al., 2006). A comprehensive survey of anomaly detection systems is presented in (Patcha & Park, 2007) and a comparison of different approaches to intrusion detection systems is given in (Bejtlich, 2004). One of the first agent systems for network security monitoring has been proposed in works (Balasubramaniyet et al., 1998, Spafford & Zamboni, 2000). In work (Kolaczek et al., 2005) a framework of an original proposal of the intrusion detection system based on the multi-agent approach was presented. In particular, the architecture of such a system and the task of agents were specified. Proposed ideas were further developed and in work (Nguyen et al., 2006) the problem of anomalies detection on the basis of the nodes traffic analysis was discussed. The proposal of the method for Denial of Service Attack detection was given in (Prusiewicz, 2008a). In this work we propose a novel framework of a multi-agent system for anomaly detection. The originality of our solution consists of applying the social network approach to Man in the Middle Attack (MITM) detection in a network system. Our proposal is based on the social networks discovery and their characteristics measurement to detect anomalies in network traffic. We assume that network communication between nodes constitutes social network of users and their applications, so the appropriate methods of social network formal analysis can be applied. The other important assumption is that values of these social

With the rapid expansion of digital networks and the increasing complexity of cyber threats, network security has emerged as a crucial field within information and communications technology (ICT). Modern organizations face growing risks from sophisticated cyber-attacks that threaten the confidentiality, integrity, and availability of critical systems. Intrusion Detection Systems (IDS) have become a foundational tool for identifying and mitigating unauthorized access and suspicious activities within networks. These systems are broadly categorized into Signature-Based Intrusion Detection Systems (SIDS), which rely on known threat patterns, and Anomaly-Based Intrusion Detection Systems (AIDS), which detect deviations from normal behavior to identify unknown attacks. Despite their strengths, both types face significant limitations, including high false-positive rates and challenges in real-time detection. This study explores the evolving landscape of network security threats and critically analyzes existing intrusion detection techniques. It highlights the integration of alert correlation and prediction mechanisms that enhance early detection and response capabilities. Furthermore, the study addresses key limitations and challenges in IDS implementation and identifies emerging trends aimed at improving scalability, intelligence, and adaptability of detection mechanisms. By evaluating current systems and proposing directions for future research, this work contributes to the development of more robust and proactive network defense strategies in an increasingly interconnected digital world.

Internet attacks have become more sophisticated over time, and they can now circumvent basic security measures like antivirus scanners and firewalls. Identifying, detecting, and avoiding breaches is essential for network security in today's computing world. Adding an extra layer of defence to the network infrastructure through an Intrusion Detection System is one approach to improve network security. Anomaly-based or signature-based detection algorithms are used by existing Intrusion Detection Systems (IDS). Signature-based IDS, for example, detects attacks based on a set of signatures but is unable to detect zero day attacks. In contrast, anomaly-based IDS analyses deviations in behaviour and can detect unexpected attacks. This study suggests designing and developing an Advanced signature-based Intrusion Detection System for Improved Performance by Combining Signature and Anomaly-Based Approaches. It includes three essential stages, first Signature-based IDS used for checking the attacks from the Signature Ruleset using Decision Tree received accuracy 96.96%, and the second stage Anomaly-based IDS system used Deep learning technique ResNet50. The model relies on ResNet50, a Convolutional Neural Network with 50 layers that received an accuracy of 97.25%. By classifying all network packets into regular and attack categories, the combination of both detect known and unknown attacks is the third stage and generates signature from anomaly-based IDS. It gives the accuracy of 98.98% for detection of intrusion. Here findings show that the suggested intrusion detection system may efficiently detect real-world intrusions.KeywordsNetwork securityIntrusion detection systemMachine learningDecision tree

The Internet of Things (IoT) has been rapidly evolving towards making a greater impact on everyday life to large industrial systems. Unfortunately, this has attracted the attention of cybercriminals who made IoT a target of malicious activities, opening the door to a possible attack to the end nodes. Due to the large number and diverse types of IoT devices, it is a challenging task to protect the IoT infrastructure using a traditional intrusion detection system. To protect IoT devices, a novel ensemble Hybrid Intrusion Detection System (HIDS) is proposed by combining a C5 classifier and One Class Support Vector Machine classifier. HIDS combines the advantages of Signature Intrusion Detection System (SIDS) and Anomaly-based Intrusion Detection System (AIDS). The aim of this framework is to detect both the well-known intrusions and zero-day attacks with high detection accuracy and low false-alarm rates. The proposed HIDS is evaluated using the Bot-IoT dataset, which includes legitimate IoT network traffic and several types of attacks. Experiments show that the proposed hybrid IDS provide higher detection rate and lower false positive rate compared to the SIDS and AIDS techniques.

The Internet of Things (IoT) has become increasingly popular, and opened new possibilities for applications in various domains. However, the IoT also poses security challenges due to the limited resources of the devices and its dynamic network topology. Routing attacks on 6LoWPAN-based IoT devices can be particularly challenging to detect because of its unique characteristics of the network. In recent years, several techniques have been proposed for detecting routing attacks, including anomaly detection. These techniques leverage different features of network traffic to identify and classify routing attacks. This paper focuses on routing attacks that target the Routing Protocol for Low-Power and Lossy Networks (RPL), which are widely used in 6LoWPAN-based IoT systems. The attacks discussed in this paper can be categorized as either inherited from Wireless Sensor Networks or exploiting vulnerabilities unique to RPL (known as RPL-specific attacks). The paper describes various RPL attacks, including Flood Attacks, Data-DoS/DDoS Attacks, Wormhole Attacks, RPL Rank Attacks, Blackhole Attacks, Version Attacks, and Sinkhole Attacks. In this paper, a novel Hybrid Intrusion Detection System (HIDS) that combines a decision tree classifier and a one-class Support Vector Machine classifier is proposed to detect routing attacks. The HIDS draws on the strengths of both a Signature Intrusion Detection System (SIDS) and an Anomaly-based Intrusion Detection System (AIDS) to identify routing attacks with a high degree of accuracy and a low false alarm rate. The routing dataset, which features genuine IoT network traffic and various kinds of routing attacks, was used to test the proposed HIDS. According to the findings, the hybrid IDS proposed in this study outperforms SIDS and AIDS approaches, with higher detection rates and lower false positive rates.

Intrusion detection system (IDS) is an important part of enterprise security system architecture. In particular, anomaly-based IDS has been widely applied to detect single abnormal process events that deviate from the majority. However, intrusion activity usually consists of a series of low-level heterogeneous events. The gap between low-level process events and high-level intrusion activities makes it particularly challenging to identify process events that are truly involved in a real malicious activity, and especially considering the massive 'noisy' events filling the event sequences. Hence, the existing work that focus on detecting single events can hardly achieve high detection accuracy. In this work, we formulate a novel problem in intrusion detection - suspicious event sequence discovery, and propose GID, an efficient graph-based intrusion detection technique that can identify abnormal event sequences from massive heterogeneous process traces with high accuracy. We fully implement GID and deploy it into a real-world enterprise security system, and it greatly helps detect the advanced threats and optimize the incident response. Executing GID on both static and streaming data shows that GID is efficient (processes about 2 million records per minute) and accurate for intrusion detection.

With the increasing rate and types of cyber attacks against information systems and communication infrastructures, many tools are needed to detect and mitigate against such attacks, for example, Intrusion Detection Systems (IDSs). Unfortunately, traditional Signature‐based IDSs (SIDSs) perform poorly against previously unseen adversarial attacks. Anomaly‐based IDSs (AIDSs) use Machine Learning (ML) and Deep Learning (DL) approaches to overcome these limitations. However, AIDS performance can be poor when trained on imbalanced datasets. To address the challenge of AIDS performance caused by these unbalanced training datasets, generative adversarial models are proposed to obtain adversarial attacks from one side and analyse their quality from another. According to extensive usage and reliability criteria for generative adversarial models in different disciplines, Generative Adversarial Networks (GANs) , Bidirectional GAN (BiGAN) , and Wasserstein GAN (WGAN) are employed to serve AIDS. The authors have extensively assessed their abilities and robustness to deliver high‐quality attacks for AIDS. AIDSs are constructed, trained, and tuned based on these models to measure their impacts. The authors have employed two datasets: NSL‐KDD and CICIDS‐2017 for generalisation purposes, where ML and DL approaches are utilised to implement AIDSs. Their results show that the WGAN model outperformed GANs and BiGAN models in binary and multiclass classifications for both datasets.

An Intrusion Detection System (IDS) is a software used to monitor a single computer or a network of computers to combat network attacks, block access to certain websites, or otherwise the attack on network protocols. The dynamic and complicated nature of cyber attacks on computer systems is beyond the capabilities of the majority of current IDS solutions. By combating intrusion attempts, network security professionals ensure that the services can be accessed at all times. One of the tools at disposal to detect and categorize suspicious behaviour is IDS. For almost 40 years, researchers in both academia and industry have been proposing strategies for detecting and avoiding such security breaches, and even constructing systems to do so. Intrusion detection systems that rely on attack signatures examine network traffic for suspicious activity. Anomaly-based intrusion detection systems, on the other hand, build a model to tell good users apart from bad ones, allowing them to spot previously unseen attacks. Machine learning (ML) techniques are increasingly being employed as a means of categorizing normal and abnormal activities. Many other ML-based intrusion detection systems have been proposed in the past few years. The purpose of this work is to provide a critical overview of the state of the art in machine learning (ML)-based intrusion detection methods. Researchers focusing on ML-based systems that detect intrusions could use this survey as a supplement to previous generic surveys on intrusion detection and a source to recent work done in the area.

An intrusion detection system (IDS) attempts to identify attacks by comparing collected data to predefined signatures known to be malicious (signature-based IDS) or to a model of legal behaviour (anomaly-based IDS). Anomaly-based approaches have the advantage of being able to detect previously unknown attacks, but they suffer from the difficulty of building robust models of acceptable behaviour which may result in a large number of false alarms. Two reasons for the large number of false alarms, caused by incorrect classification of events in current systems, one is the simplistic aggregation of model outputs inthe decision phase. The other reason is the lack of integration of additional information into the decision process. To mitigate these shortcomings, this paper proposes a two stratum Bayesian networks based anomaly detection and decision model for intrusion detection system. Bayesian networks improve the aggregation of outputs, such as empirical data and allow one to seamlessly incorporate additional information. Experimental results clearly demonstrate the efficiency of our approach to improve the accuracy of the intrusion detection and decision process in an anomaly based IDS.

Intrusion detection system (IDS) has played a central role as an appliance to effectively defend our crucial computer systems or networks against attackers on the Internet. The most widely deployed and commercially available methods for intrusion detection employ signature-based detection. However, they cannot detect unknown intrusions intrinsically which are not matched to the signatures, and their methods consume huge amounts of cost and time to acquire the signatures. In order to cope with the problems, many researchers have proposed various kinds of methods that are based on unsupervised learning techniques. Although they enable one to construct intrusion detection model with low cost and effort, and have capability to detect unforeseen attacks, they still have mainly two problems in intrusion detection: a low detection rate and a high false positive rate. In this paper, we present a new clustering method to improve the detection rate while maintaining a low false positive rate. We evaluated our method using KDD Cup 1999 data set. Evaluation results show that superiority of our approach to other existing algorithms reported in the literature.

Intrusion detection system (IDS) has played an important role as a device to defend our networks from cyber attacks. However, since it is unable to detect unknown attacks, i.e., 0-day attacks, the ultimate challenge in intrusion detection field is how we can exactly identify such an attack by an automated manner. Over the past few years, several studies on solving these problems have been made on anomaly detection using unsupervised learning techniques such as clustering, one-class support vector machine (SVM), etc. Although they enable one to construct intrusion detection models at low cost and effort, and have capability to detect unforeseen attacks, they still have mainly two problems in intrusion detection: a low detection rate and a high false positive rate. In this paper, we propose a new anomaly detection method based on clustering and multiple one-class SVM in order to improve the detection rate while maintaining a low false positive rate. We evaluated our method using KDD Cup 1999 data set. Evaluation results show that our approach outperforms the existing algorithms reported in the literature; especially in detection of unknown attacks.

Intrusion detection is an emerging area of research in the computer security and net-works with the growing usage of internet in everyday life. Most intrusion detection systems (IDSs) mostly use a single classifier algorithm to classify the network traffic data as normal behavior or anomalous. However, these single classifier systems fail to provide the best possible attack detection rate with low false alarm rate. In this paper,we propose to use a hybrid intelligent approach using a combination of classifiers in order to make the decision intelligently, so that the overall performance of the resul-tant model is enhanced. The general procedure in this is to follow the supervised or un-supervised data filtering with classifier or cluster first on the whole training dataset and then the output are applied to another classifier to classify the data. In this re- search, we applied Neural Network with Supervised and Unsupervised Learning in order to implement the intrusion detection system. Moreover, in this project, we used the method of Parallelization with real time application of the system processors to detect the systems intrusions.Using this method enhanced the speed of the intrusion detection. In order to train and test the neural network, NSLKDD database was used. Creating some different intrusion detection systems, each of which considered as a single agent, we precisely proceeded with the signature-based intrusion detection of the network.In the proposed design, the attacks have been classified into 4 groups and each group is detected by an Agent equipped with intrusion detection system (IDS).These agents act independently and report the intrusion or non-intrusion in the system; the results achieved by the agents will be studied in the Final Analyst and at last the analyst reports that whether there has been an intrusion in the system or not. Keywords: Intrusion Detection, Multi-layer Perceptron, False Positives, Signature- based intrusion detection, Decision tree, Nave Bayes Classifier

Recently, network security has become an extremely vital issue that beckons the development of accurate and efficient solutions capable of effectively defending our network systems and the valuable information journeying through them. In this article, a distributed multiagent intrusion detection system (IDS) architecture is proposed, which attempts to provide an accurate and lightweight solution to network intrusion detection by tackling issues associated with the design of a distributed multiagent system, such as poor system scalability and the requirements of excessive processing power and memory storage. The proposed IDS architecture consists of (i) the Host layer with lightweight host agents that perform anomaly detection in network connections to their respective hosts, and (ii) the Classification layer whose main functions are to perform misuse detection for the host agents, detect distributed attacks, and disseminate network security status information to the whole network. The intrusion detection task is achieved through the employment of the lightweight Adaptive Sub-Eigenspace Modeling (ASEM)-based anomaly and misuse detection schemes. Promising experimental results indicate that ASEM-based schemes outperform the KNN and LOF algorithms, with high detection rates and low false alarm rates in the anomaly detection task, and outperform several well-known supervised classification methods such as C4.5 Decision Tree, SVM, NN, KNN, Logistic, and Decision Table (DT) in the misuse detection task. To assess the performance in a real-world scenario, the Relative Assumption Model, feature extraction techniques, and common network attack generation tools are employed to generate normal and anomalous traffic in a private LAN testbed. Furthermore, the scalability performance of the proposed IDS architecture is investigated through the simulation of the proposed agent communication scheme, and satisfactory linear relationships for both degradation of system response time and agent communication generated network traffic overhead are achieved.

With the wide application of information technolo-gies in communication based train control (CB TC) systems, the information security risks it confronts to are ever increasing. It is very difficult to design an intrusion detection system (IDS) which can detect both known and unknown cyber attacks with high true positive rate (TPR) and low false positive rate (FPR), simultaneously. In this paper, we propose a hybrid intrusion detection system (RIDS) which is composed of a signature-based intrusion detection system (SIDS) and an anomaly-based intrusion detection system (AIDS). An improved stacking ensemble algorithm (ISEA) is proposed to enhance the TPR of the SIDS which uses weighted classification probabilities outputted by base-classifiers to generate meta-features for the meta-classifier. The FPR of the AIDS is significantly reduced through adopting the proposed false positive elimination strategy (FPES). In addition, a Bayesian optimization algorithm is used for hyper-parameters adjustment to optimize the overall performance of the RIDS. The proposed RIDS is evaluated using both a KDD99 dataset and a CBTC dataset collected on a hardware-in-the-Ioop simulation platform. For the KDD99 dataset, the TPR and FPR of the proposed RIDS are 98.6% and 1.3%, respectively. For the CBTC dataset, the TPR and FPR are 98.1% and 1.1 %, respectively. Based on the performance comparison among different RIDSs, it is can be concluded that the proposed RIDS is superior to the existing RIDS in both TPR and FPR.