2021 IEEE International Conference on Communications Workshops (ICC Workshops) | 978-1-7281-9441-7/20/$31.00 ©2021 IEEE | DOI: 10.1109/ICCWorkshops50388.2021.9473869 A Framework For Intelligent DDoS Attack Detection and Response using SIEM and Ontology Salva Daneshgadeh Çakmakçı Helmar Hutschenreuter University of Bremen Bremen, Germany salva@uni-bremen.de Abstract—In this paper, we propose an intelligent DDoS detection and response framework. It employs a Security Information and Event Management (SIEM) tool to detect different types of DDoS attacks using its incident detection engine. Additionally, it has an inference engine to automatically infer potential countermeasures to respond to and recover from DDoS attacks. The inference system continuously reasons for each reported incident and provides suggestions to keep the system stable. We model explicit knowledge of an IT-dependent organization at a high-level using ontologies for the organization, IT, security, and DDoS attacks. We demonstrate the connections of these ontologies with the inference system and a SIEM. This paper is a part of ongoing research for securing the maritime port ecosystem. The proposed framework not only automates the detection of DDoS attacks but also supports the implementation of automatic countermeasures. The framework can be used as a guide for cyber attack resilience in IT-dependent organizations by preventing, detecting, responding to and recovering from different types of cyber attacks. Index Terms—SIEM, Ontology, Inference System, Intelligent Attack Detection, DDoS Response, DDoS Recovery I. I NTRODUCTION Distributed Denial of Service (DDoS) is one of the relatively old, but still effective attack techniques. DDoS attacks are very popular because DDoS tools are usually easy to access and launch, but they can cause catastrophic effects on networks. DDoS attacks target the availability of internet-based services and applications. Many types of DDoS attacks such as flood and amplification attacks cause a huge volume of traffic or broadcast on an IP address to bombard a victim’s machine and consume its bandwidth. As a result, the victim’s machine is overwhelmed by fake traffic that is similar to real one. This similarity between DDoS attacks and real traffic makes it difficult to distinguish legitimate user traffic from attacks. According to Corero [1], the frequency of DDoS attacks and their complexity tend to increase while their size and duration decrease. Academia and industry investigated mainly DDoS attack detection mechanisms while neglecting response and recovery for cyber resilience. At best a list of countermeasures, to be applied manually by skilled individuals, are provided. A. Ontology An ontology is a “specific, formal representation of a shared conceptualization of a domain” [2]. An ontology defines the explicit knowledge associated with specific objects in a 978-1-7281-9441-7/21/$31.00 ©2021 IEEE Christian Maeder Thomas Kemmerich University of Bremen University of Bremen University of Bremen Bremen, Germany Bremen, Germany Bremen, Germany hutschen@uni-bremen.de c.maeder@uni-bremen.de thomas.kemmerich@uni-bremen.de machine-readable form. Ontologies may support communication, inference and reuse; informal ontologies are represented by natural languages [3]. However, ontologies should be written in a formal language like the Web Ontology Language (OWL). OWL is the most popular web ontology language with semantics that support deriving knowledge by logical inferences using automated reasoners. Although OWL does not have a clear separation between TBoxes and ABoxes [4], it makes sense to conceptually distinguish these kinds of knowledge. A TBox mainly describes static knowledge (e.g., classes and properties) whereas an ABox concentrates on dynamic and frequently changing knowledge (e.g., objects of classes or individuals). B. Artificial Intelligence and Ontology Gruber [5] defined an ontology as a set of representational terms in the context of Artificial Intelligence (AI). In this fashion, an ontology formally specifies the concepts of an interesting domain with human-readable text where the relationships, constraints and well-defined uses of terms are explicitly expressed. Ontologies are used for organizing information and representing knowledge for systems based on AI [6]. In recent years, ontologies have been used in many domains such as health care, industrial control systems and environmental monitoring to elicit useful knowledge from collected data. Ontologies can actually fill in the gap between data generation and usage. Razzaq et al. [7] proposed an intelligent ontology-based application-level Intrusion Detection System (IDS) using a Bayesian filter to protect zeroday attacks. The rule engine of their proposed IDS was able to communicate with a knowledge-base and to automatically generate rules against web application attacks. Roda and Musulin [8] proposed an ontology-based framework with symbol-based reasoning. Their framework utilizes semantic technologies to describe the state or condition of a dynamic process. Subsequently, these descriptions are used to analyze raw sensor data for the detection of errors, problems or faults. Khairkar et al. [9] made a literature review on different types of traditional and AI-enabled intrusion detection systems and discussed that there is a need for an intrusion detection system that is able to understand the context of the attack and the target domain for making intelligent decisions. They suggested the usage of semantic web and ontology concepts for analyzing Authorized licensed use limited to: Nottingham Trent University. Downloaded on October 18,2023 at 00:55:17 UTC from IEEE Xplore. Restrictions apply. security logs, for raising alarms and for giving real-time responses, but provided no guideline to develop such a system. Pardo et al. [10] proposed a context-aware anomaly detection framework for smart homes. Their framework uses ontologies to detect (hardware, software, network, operator and context) anomalies and respond to them. Ontological-based cybersecurity is a relatively new approach in the literature especially when it comes to intelligent attack detection using ontologies. Recently, Hutschenreuter et al. [11] proposed an ontology-based cybersecurity and resilience framework to prevent, detect, respond to and recover from cyber incidents. C. DDoS Attack Detection We classify DDoS attack detection mechanisms into three groups: signature-based, systematic, and intelligent. A signature-based detection compares the characteristics of the captured traffic to the well-defined characteristics of previous attacks (e.g., IDS). Statistical analysis (e.g., moving average) and information theory (e.g., Shannon entropy) are well-known examples of systematic mechanisms (see [12]– [14]). Intelligent detection algorithms employ techniques like Machine Learning (ML) [15]–[17], Deep Learning (DL) [18], [19], and ontologies [20]–[22] to model the behavior of attacks using feature vectors (for ML and DL) and the knowledge about attacks and their environments (for ontologies). Intelligent detection algorithms are suitable to detect zero-day attacks but exhibit high false-alarm rates. D. Our Contribution This study presents a novel intelligent DDoS attack detection framework by integrating SIEM, state-of-the-art security tools, ontologies and logical inferences to detect and countermeasure DDoS attacks. Ontologies feed an inference engine to select the most appropriate DDoS recovery and response measures in an intelligent manner. As a result, the human error-prone and time-consuming tasks of attack response and recovery are automated and accelerated. The proposed framework can be used to detect different types of attacks in different domains and applications only by updating a knowledge-base containing knowledge of attack types, the IT infrastructure and its environment. The knowledge-base can also be updated by lessons learned from former attacks. II. P ROPOSED F RAMEWORK Our proposed algorithm combines three components: Security Tools like firewalls, anti-virus, IDS/IPS, and SIEM for DDoS attack detection, Ontologies, and an Inference System for automatic response and recovery (Figure 2). A. SIEM Security Event and Information Management (SIEM) is a security technology that ingests events and logs from different sources like applications, systems, and network components. Logs are parsed and normalized and can be collected by an agent-based method, that requires agent software on all TABLE I DD O S DETECTION METHODS . Features Ng Technique Rule-based Ng Correlation M eanN g Ng Statistical ML Ng , EIP Anomaly DDoS attack condition Ng > 1000 Ng > 1000 and some IP addresses that are suspicious based on threat intelligence Ng > 1.5 ∗ M eanN g Support Vector Machine Algorithm [24] E-KOAD devices, or by an agent-less method, where embedded devices like routers, printers, or a firewall send their logs to a remote data collector [23]. Preprocessing converts non-structural logs into a common format that can be consumed by an intrusion detection engine. Logs are usually given as plain text and a parser (regular expression) separates different fields inside a log. Finally, field names and data are normalized and sent to the intrusion detection engine to spot potential attacks (see Figure 1). The intrusion detection module consists of simple correlation rules (correlating events from different sources) or uses more advanced techniques like statistical analysis, ML, DL, or anomaly detection. Table I gives an overview of different algorithms that can be part of the intrusion detection engine to detect DDoS attacks. The number of HTTP GET requests from a web application is denoted by Ng , whereas M eanN g denotes the mean number of requests from previous days for a statistical analysis. The Kernel Online Anomaly Detection (KOAD) [17] considers the entropy of IP addresses (EIP ) and the Mahalanobis distance. The command and execution module is responsible for configuring the IT infrastructure. It receives inferred measures from the inference system and applies them as a command script. Commands may change access control policies or apply management actions (e.g., block user accounts , change router configurations [25]. B. DDoS Detection by SIEM This section presents a detailed example of how network flow data is used by a SIEM to detect abnormal activities that may be DDoS attacks. A complete guideline to utilize and adjust a SIEM is beyond the scope of this paper. For demonstration, we used the normal and DDoS traffic data from the CIC-IDS2017 [26] benchmark dataset. It includes traffic flow based on captured network traffic (PCAP). The CICFlowMeter [27] was used to create attributes like timestamps, source and destination IP addresses, ports, protocols, etc. In practice, any network flow capturing tool like NetFlow [28] can be used to collect network flows based on the IP addresses that enters an organization’s interface. Here, we directly uploaded related CSV files to the free and open Elastic SIEM [29]. We did not use any machine learning or anomaly detection capability of SIEM’s analytical engine to detect DDoS attacks. The aim of this use case is to show that a skilled security analyst Authorized licensed use limited to: Nottingham Trent University. Downloaded on October 18,2023 at 00:55:17 UTC from IEEE Xplore. Restrictions apply. Fig. 1. Example of raw and normalized firewall logs. between classes. Soft-IT and Hard-IT are connected via the Device class. Therefore, instances of the classes Subject and Object will be assigned to IT devices from the Hard-IT infrastructure. In practice, both an ABox and the TBox of the ontology should be modeled for a complete knowledge base. ABoxes contain concrete instances of the classes and roles. For example, there may be two instances of the class User (U1 and U2) and one instance of the class Group (G1). Subsequently, the member role could be used to assign both users to the same group G1 to indicate that users U1 and U2 have equal group privileges. Our TBox describes the high level and the general IT infrastructure of an organization, therefore it can be basically reused for IT infrastructure of other organizations. On the other hand, an ABox completely depends on the actual IT infrastructure of an organization. The following box shows a small part of an ABox created using Python and the library ”Owlready2” [31]. Fig. 2. Proposed intrusion detection and response framework. might manually explore data using the visualization features of Kibana [30] and write pre-built rules to detect anomalies or attacks. Figure 3 clearly demonstrate the abnormal behavioral of network traffic between the timestamps 4:00 and 4:15. The SIEM supports simple threshold settings for an alarming network traffic that indicates a DDoS attack. For instance, one can add a query rule that raises a DDoS alarm if the number of connections per minute increases to three times of the average number from the last hour. C. Ontology of IT Infrastructures The formal model of an IT infrastructure encompasses the explicit knowledge of an IT system and its environment inside an organization. Figure 4 shows a corresponding TBox with subclasses Hard-IT and Soft-IT. Soft-IT describes operating systems, applications, and virtual machines that provide services or are used by employees to access stored data. Hard-IT represents the physical infrastructure like devices (e.g., PCs, routers), links (e.g., wired or wireless), and the network (e.g., inter- or intranet). The security measures protected both Softand Hard-IT infrastructures. Dotted lines indicate inheritance between classes. Roles are depicted by solid arrows and represent the relationships managing director pc = PC(“managing director pc”) it administrator pc = PC(“it administrator pc”) employees pc1 = PC(“employees pc1”) employees pc2 = PC(“employees pc2”) mail server = Server(“mail server”) employee1 = User(“employee1”) employee2 = User(“employee2”) employees = Group(“employees”) mail group = Group(“mail group”) management = Group(“management”) it administrator = User(“it administrator”) it administrators = Group(“it administrators”) mail service = Service(“mail service”) customer data = Data(“customer data”) personnel data = Data(“personnel data”) wlan access point = AccessPoint(“wlan access point”) wlan access point.linkToDevices(WirelessLink, Intranet(“lan”), managing director pc, it administrator pc, employees pc1, employees pc2) employees.addUsers(employee1,employee2) employees.ValidForDevices(mail server, employees pc1, employees pc2) mail group.ValidForDevices(mail server) mail server.hostsObjects(mail service, mails) management.permitAccessToObjects(customer data, personnel data, mail service) D. Ontology of Cybersecurity The bottom left part of Figure 5 shows the three organizational classes BusinessProcess, Role and Employee. Business processes need infrastructures to be run on and the responsibility for infrastructures is controlled by roles given to employees. The TBox for cybersecurity can also be used for any organization or application scenario. Security measures reduce threats and support security objectives that are threatened by threats. Our security ontology describes Authorized licensed use limited to: Nottingham Trent University. Downloaded on October 18,2023 at 00:55:17 UTC from IEEE Xplore. Restrictions apply. (a) Total number of destination IP addresses per minute (b) Mean of Average Inter Arrival Time (IAT) for flows per minute Fig. 3. Network traffic bar graph presentations created using Kiban queries. Fig. 4. TBox for an IT infrastructure. which infrastructure should be protected by which security measure. The classes ManualMeasure and TechnicalMeasure are subclasses of the class ResponseRecoveryMeasure. They are used to differentiate between technical (e.g., changing a firewall rule) and manual measures (e.g., more investigation by a cybersecurity analyst). The role integratesTechnicalMeasure and its inverse role isIntegratedByInfrastructure shows the application of technical measures to the infrastructure. E. Ontology of DDoS Attacks Figure 6 demonstrates a general TBox for DDoS attacks that consists of the classes Attack and Technology. The class DDoS is a subclass of Attack and has two more subclasses BandwidthExhaustion and ResourceExhaustion. Bandwidth exhaustion overwhelms a network with unwanted traffic and resource exhaustion consumes a noticeable amount of resources. Both types of attack can target a server or a process of a victim and prevent responses to legitimate requests [32]. The DDoS attacks are further classified by the subclasses Flood, Amplification, ProtocolExploit and MalformedPacket. F. Inference System Given TBoxes and ABoxes for all ontologies described above, the inference system is able to determine which business processes are working and which security objects are met. As an inference engine an OWL reasoner like HermiT [33] that comes with Protégé [34] is expected to work for our purposes. For an attack the consequences for the infrastructure can be derived. The degraded infrastructure in turn determines the affected business processes and security objectives. From a larger set of a priori known measures, those measures can be inferred that counter the degrading effects. An actual choice of a measure or several measures will be based on some simulation. A measure is temporarily added as a new fact to the formal model and consequences are derived anew. Only if this leads to an improvement, the measure will actually be proposed or automatically taken. III. F RAMEWORK IN P RACTICE The DDoS detection module of SIEM analyzes different logs from different resources using its built-in DDoS detection algorithms and raises an alarm when it detects a DDoS attack against one of the servers or web-based Authorized licensed use limited to: Nottingham Trent University. Downloaded on October 18,2023 at 00:55:17 UTC from IEEE Xplore. Restrictions apply. Fig. 5. TBox for Cybersecurity. • • • • • • • • • • Fig. 6. TBox for DDoS attack. applications. Consequently, a notification message which includes information about the attack type and the system (Hard- or Soft-IT infrastructure) under attack is sent to the inference system. Finally, the inference system takes the following steps to suggest countermeasures. 1) A DDoS attack is added with its type and initial target as a fact to the formal ontology model. 2) The impact of the attack on connected parts of the infrastructure and on business processes can be derived. Also the possibility of co-occurring attacks could be considered if suitably modeled in the ontology. 3) Potential measures to respond to or recover from the given DDoS (and possible co-occurring) attacks will be suggested. 4) The effectiveness of a measure is tested by temporarily adding the measure as a fact to the underlying formal model. 5) Only if the extended ontology improves the situation for business processes and security objectives, the measure is sent as effective measure to the SIEM. The measure is kept in the formal model as long as the causing degradation of the infrastructure persists. 6) The steps 4 to 5 are repeated as long as the situation improves and no further risks threaten business processes. A. DDoS Attack Countermeasures The inference system sends a message for each effective measure to the SIEM. The potential list of response and recovery messages are as following [21], [32], [35]: Filter the attack streams. Enable privileged access (e.g., IP-based). Block IP addresses with suspicious geo-location info. Increase bandwidth of connections. Locate proxy servers in front of the server. Distribute arriving requests between proxy servers via the load balancer. Enlarge the backlog queue for requests. Increase the timeout of connections in backlog. Check for other potential attacks. Inform responsible people or authorities. The inference system suggests the most compatible measures because it has the knowledge about the IT infrastructure, security objectives, DDoS types, and measures. For example, if a detection algorithm is able to distinguish DDoS attacks from Flash Events (FE) [36], then the inference system will send a “Increase Bandwidth” message for a FE incident and a “Block Suspicious IP Addresses” message for a DDoS attack. The inference system might suggest to investigate potential concurrent attacks like data ex-filtration. According to [37] small DDoS attacks may be used to distract staff and launch a main attack. IV. D ISCUSSION According to Gartner, worldwide information security expenditure will reach $170.4 billion in 2022. Phishing, whaling, malware, social engineering, ransomware and DDoS attacks are among the top common cyber security attacks in different fields like healthcare, finance, or governments [38]. The fundamental knowledge for the detection of mentioned attacks is almost identical for all organizations and domains. Ontologies can grasp, share, and reuse this common information security knowledge (IT assets, attack types, protective measures, attack countermeasures, and so on) thus avoiding duplicated efforts and rebuilding everything from scratch. However, the elementary knowledge-base should keep up with new IT technologies and their vulnerabilities or with special security requirements of individual or sector-based organizations. The ultimate goal Authorized licensed use limited to: Nottingham Trent University. Downloaded on October 18,2023 at 00:55:17 UTC from IEEE Xplore. Restrictions apply. of our proposed framework is to formalize and represent the concepts of common knowledge in the field of attack detection. V. C ONCLUSION AND F UTURE W ORK The ontologies for IT infrastructures, cybersecurity, and DDoS attacks create a powerful construct for selecting appropriate recovery and response measures for various kinds of DDoS attacks. Our proposed framework opens areas for further research for example for extending the ontologies, modeling different attacks and finding an efficient protocol for the communication between SIEM and the inference system or developing an ontology-based SIEM. Our framework could be a cost-effective approach to increase the automation level of cybersecurity in different industries and compensate for the lack of security specialists. The approach only requires the modeling of some organization-specific knowledge in addition to given security tools and a SIEM. The detailed modeling of ABoxes and experimental evaluation of the proposed algorithm is left for future work. ACKNOWLEDGMENTS This work was supported by the German Federal Ministry of Transport and Digital Infrastructure (BMVI) under the grant 19H18012E (SecProPort project). R EFERENCES [1] Corero, “H1 trends report summary of inputs,” 2020. [Online]. Available: https://go.corero.com/corero-h1-2020-trends-report-download [2] M. Uschold and M. Gruninger, “Ontologies: Principles, methods and applications,” The Knowledge Engineering Review, vol. 11, no. 2, pp. 93–136, 1996. [3] V. Nguyen, “Ontologies and information systems: a literature survey,” Australia: DSTO Defence Science and Technology Organisation, 2011. [4] S. Brockmans, R. Volz, A. Eberhart, and P. Löffler, “Visual modeling of OWL DL ontologies using UML,” in International Semantic Web Conference. Springer, 2004, pp. 198–213. [5] T. R. Gruber, “Toward principles for the design of ontologies used for knowledge sharing?” International Journal of Human-Computer Studies, vol. 43, no. 5, pp. 907–928, 1995. [Online]. Available: http://www.sciencedirect.com/science/article/pii/S1071581985710816 [6] W. S. Mark, T. Donneau-Golencer, and M. Yarlagadda, “Adaptive ontology,” 2014, US Patent 8,918,431. [7] A. Razzaq, H. F. Ahmed, A. Hur, and N. Haider, “Ontology based application level intrusion detection system by using bayesian filter,” in 2009 2nd International Conference on Computer, Control and Communication, 2009, pp. 1–6. [8] F. Roda and E. Musulin, “An ontology-based framework to support intelligent data analysis of sensor measurements,” Expert Systems with Applications, vol. 41, no. 17, pp. 7914–7926, 2014. [9] A. D. Khairkar, D. D. Kshirsagar, and S. Kumar, “Ontology for detection of web attacks,” in 2013 International Conference on Communication Systems and Network Technologies. IEEE, 2013, pp. 612–615. [10] E. Pardo, D. Espes, and P. Le Parc, “A framework for anomaly diagnosis in smart homes based on ontology,” in The 7th International Conference on Ambient Systems, Networks and Technologies (ANT 2016), 2016. [11] H. Hutschenreuter, S. D. Çakmakçı, C. Maeder, and T. Kemmerich, “Ontology-based cybersecurity and resilience framework,” in 7th International Conference on Information Systems Security and Privacy, 2021, accepted. [12] S. M. T. Nezhad, M. Nazari, and E. A. Gharavol, “A novel DoS and DDoS attacks detection algorithm using arima time series model and chaotic system in computer networks.” IEEE Communications Letters, vol. 20, no. 4, pp. 700–703, 2016. [13] M. H. Bhuyan, D. Bhattacharyya, and J. K. Kalita, “An empirical evaluation of information metrics for low-rate and high-rate DDoS attack detection,” Pattern Recognition Letters, vol. 51, pp. 1–7, 2015. [14] S. Behal, K. Kumar, and M. Sachdeva, “D-FACE: An anomaly based distributed approach for early detection of DDoS attacks and flash events,” Journal of Network and Computer Applications, vol. 111, pp. 49–63, 2018. [15] Y. Gu, K. Li, Z. Guo, and Y. Wang, “Semi-supervised k-means DDoS detection method using hybrid feature selection algorithm,” IEEE Access, vol. 7, pp. 64 351–64 365, 2019. [16] G. Fernandes Jr, L. F. Carvalho, J. J. Rodrigues, and M. L. Proença Jr, “Network anomaly detection using ip flows with principal component analysis and ant colony optimization,” Journal of Network and Computer Applications, vol. 64, pp. 1–11, 2016. [17] S. D. Çakmakçı, T. Kemmerich, T. Ahmed, and N. Baykal, “Online DDoS attack detection using mahalanobis distance and kernel-based learning algorithm,” Journal of Network and Computer Applications, vol. 168, no. 102756, 2020. [18] X. Yuan, C. Li, and X. Li, “DeepDefense: Identifying DDoS attack via deep learning,” in International Conference on Smart Computing (SMARTCOMP). IEEE, 2017, pp. 1–8. [19] Q. Niyaz, W. Sun, and A. Y. Javaid, “A deep learning based DDoS detection system in software-defined networking (SDN),” EAI Endorsed Transactions on Security and Safety, vol. 4, no. 12, 2017. [20] J. Pinkston, J. Undercoffer, A. Joshi, and T. Finin, “A target-centric ontology for intrusion detection,” in IJCAI Workshop on Ontologies in Distributed Systems, 18th International Joint Conference on Artificial Intelligence, 2003. [21] S. Ramanauskaite and A. Cenys, “Taxonomy of DoS attacks and their countermeasures,” Open Computer Science, vol. 1, no. 3, pp. 355–366, 2011. [22] A. Razzaq, Z. Anwar, H. F. Ahmad, K. Latif, and F. Munir, “Ontology for attack detection: An intelligent approach to web application security,” computers & security, vol. 45, pp. 124–146, 2014. [23] NXLog, “Agent-based versus agent-less log collection — which option is best?” 2019. [Online]. Available: https://nxlog.co/agent-based-versusagent-less [24] S. Daneshgadeh, N. Baykal, and Ş. Ertekin, “DDoS attack modeling and detection using SMO,” in 16th International Conference on Machine Learning and Applications (ICMLA). IEEE, 2017, pp. 432–436. [25] G. G. Granadillo, Y. B. Mustapha, N. Hachem, and H. Debar, “An ontology-based model for siem environments,” in Global Security, Safety and Sustainability & e-Democracy. Springer, 2011, pp. 148–155. [26] CIC, “Intrusion detection evaluation dataset,” 2017. [Online]. Available: https://www.unb.ca/cic/datasets/ids-2017.html [27] CIC, “Cicflowmeter,” 2020. [Online]. Available: https://github.com/CanadianInstituteForCybersecurity/CICFlowMeter [28] CISCO, “Introduction to cisco ios netflow - a technical overvie,” 2012. [29] Elastic, “Siem at the speed of elasticsearch.” [Online]. Available: https://www.elastic.co/siem [30] Elastic, “Your window into the elastic stack.” [Online]. Available: https://www.elastic.co/kiban [31] J.-B. Lamy, “Owlready: Ontology-oriented programming in python with automatic classification and high level constructs for biomedical ontologies,” Artificial intelligence in medicine, vol. 80, pp. 11–28, 2017. [32] S. Specht and R. Lee, “Taxonomies of distributed denial of service networks, attacks, tools and countermeasures,” CEL2003-03, Princeton University, Princeton, NJ, USA, 2003. [33] HermiT, “HermiT OWL Reasoner,” 2013. [Online]. Available: http://www.hermit-reasoner.com [34] M. A. Musen, “The Protégé project: A look back and a look forward,” AI Matters, vol. 1, no. 4, pp. 4–12, 2015. [35] H. Beitollahi and G. Deconinck, “Analyzing well-known countermeasures against distributed denial of service attacks,” Computer Communications, vol. 35, no. 11, pp. 1312–1332, 2012. [36] S. Daneshgadeh, T. Ahmed, T. Kemmerich, and N. Baykal, “Detection of DDoS attacks and flash events using shannon entropy, KOAD and mahalanobis distance,” in 22nd Conference on Innovation in Clouds, Internet and Networks and Workshops (ICIN). IEEE, 2019, pp. 222– 229. [37] Corero, “Corero & GTT DDoS trends report Q2–Q3 2017.” [Online]. Available: https://www.gtt.net/media/1443/corero-q2-q3-trendreports.pdf [38] Statistic, “134 cybersecurity statistics and trends for 2021.” [Online]. Available: https://www.varonis.com/blog/cybersecurity-statistics/ Authorized licensed use limited to: Nottingham Trent University. Downloaded on October 18,2023 at 00:55:17 UTC from IEEE Xplore. Restrictions apply.