Mitigating Coordinated Call Attacks On VoIP Networks Using Hidden Markov Model

Abstract This paper presents a 2-tier scheme for mitigating coordinated call attacks on VoIP networks. Call interaction pattern was considered using talk and salient periods in a VoIP call conversation. At the first-tier, Short Term Energy algorithm was used for call interaction feature extraction and at the second-tier Hidden Markov Model was used for caller legitimacy recognition. Data of VoIP call conversations were collated and analyzed to extract distinctive features in VoIP call interaction pattern to ascertain the legitimacy of a caller against coordinated call attacker. The performance metrics that was used are; False Error Rate (FER), Specificity, Detection Accuracy and Throughput. Several experiments were conducted to see how effective the mitigating scheme is, as the scheme acts as a proxy server to Session Initiation Protocol (SIP) server. The experiments show that; when the VoIP server is under coordinated call attack without a mitigating scheme only 15.2% of legitimate VoIP users had access to the VoIP network and out of which about half of the legitimate users had their calls dropped before completion, while with the 2-tier mitigating scheme, when the VoIP server is under coordinated call attacks over 90.3% legitimate VoIP callers had their calls through to completio

Cybersecurity analysis of a SCADA system under current standards, client requisites, and penetration testing

Supervisory Control and Data Acquisition (SCADA) systems are essential for monitoring and controlling a country's Critical Infrastructures (CI) such as electrical power grids, gas, water supply, and transportation services. These systems used to be mostly isolated and secure, but this is no longer true due to the use of wider and interconnected communication networks to reap benefits such as scalability, reliability, usability, and integration. This architectural change together with the critical importance of these systems made them desirable cyber-attack targets. Just as in other Information Technology (IT) systems, standards and best practices have been developed to provide guidance for SCADA developers to increase the security of their systems against cyber-attacks.With the assistance of EFACEC, this work provides an analysis of a SCADA system under current standards, client requisites, and testing of vulnerabilities in an actual prototype system. Our aim is to provide guidance by example on how to evaluate and improve the security of SCADA systems, using a basic prototype of EFACEC's ScateX# SCADA system, following both a theoretical and practical approach. For the theoretical approach, a list of the most commonly adopted ICS (Industrial Control Systems) and IT standards is compiled, and then sets of a generic client's cybersecurity requisites are analyzed and confronted with the prototype's specifications. A study of the system's architecture is also performed to identify vulnerabilities and non-compliances with both the client's requisites and the standards and, for the identified vulnerabilities, corrective and mitigation measures are suggested. For the practical approach, a threat model was developed to help identify desirable assets on SCADA systems and possible attack vectors that could allow access to such assets. Penetration tests were performed on the prototype in order to validate the attack vectors, to evaluate compliance, and to provide evidence of the effectiveness of the corrective measures

The Journal of Mine Action Issue 6.2 (2002)

Landmines in Afric

Making sense of mixtures : chromatographic separations of plant, insect and microbial biomolecules.

Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1996.No abstract available