A Robust Mechanism for Defending Distributed Denial OF Service Attacks on Web Servers

Distributed Denial of Service (DDoS) attacks have emerged as a popular means of causing mass targeted service disruptions, often for extended periods of time. The relative ease and low costs of launching such attacks, supplemented by the current inadequate sate of any viable defense mechanism, have made them one of the top threats to the Internet community today. Since the increasing popularity of web-based applications has led to several critical services being provided over the Internet, it is imperative to monitor the network traffic so as to prevent malicious attackers from depleting the resources of the network and denying services to legitimate users. This paper first presents a brief discussion on some of the important types of DDoS attacks that currently exist and some existing mechanisms to combat these attacks. It then points out the major drawbacks of the currently existing defense mechanisms and proposes a new mechanism for protecting a web-server against a DDoS attack. In the proposed mechanism, incoming traffic to the server is continuously monitored and any abnormal rise in the inbound traffic is immediately detected. The detection algorithm is based on a statistical analysis of the inbound traffic on the server and a robust hypothesis testing framework. Simulations carried out on the proposed mechanism have produced results that demonstrate effectiveness of the proposed defense mechanism against DDoS attacks.Comment: 18 pages, 3 figures, 5 table

A Proactive DOS Filter Mechanism for Delay Tolerant Networks

Denial of Service (DOS) attacks are a major threat faced by all types of networks. The effect of DOS in a delay tolerant network (DTN) is even more aggravated due to the scarcity of resources. Perpetrators of DOS attacks in DTN-like environments look beyond the objective of rendering a target node useless. The aim of an attacker is to cause a network-wide degradation of resources, service and performance. This can easily be achieved by exhausting node or link resources and partitioning the network. In this paper we seek to provide a proactive approach in making the DTN authentication process robust against DOS. Our aim is to make security protocols which provide mandatory DTN security services resilient to DOS attacks. The overall objective is to make it hard to launch a DOS attack and ensure the availability of DTN services. A DTN-cookie mechanism has been proposed to quickly identify and filter out illegitimate traffic

Estudio de propiedades estáticas y dinámicas para modelos aplicados a redes de comunicaciones

Tesis inédita de la Universidad Autónoma de Madrid. Escuela Técnica Superior de Informática, Departamento de Ingeniería informática. Fecha de lectura: 14-06-200

Security plane for data authentication in information-centric networks

Orientadores: Maurício Ferreira Magalhães, Jussi KangasharjuTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: A segurança da informação é responsável pela proteção das informações contra o acesso nãoautorizado, uso, modificação ou a sua destruição. Com o objetivo de proteger os dados contra esses ataques de segurança, vários protocolos foram desenvolvidos, tais como o Internet Protocol Security (IPSEC) e o Transport Layer Security (TLS), provendo mecanismos de autenticação, integridade e confidencialidade dos dados para os usuários. Esses protocolos utilizam o endereço IP como identificador de hosts na Internet, tornando-o referência e identificador no estabelecimento de conexões seguras para a troca de dados entre aplicações na rede. Com o advento da Web e o aumento exponencial do consumo de conteúdos, como vídeos e áudios, há indícios da migração gradual do uso predominante da Internet, passando da ênfase voltada para a conexão entre hosts para uma ênfase voltada para a obtenção de conteúdo da rede, paradigma esse conhecido como information-centric networking. Nesse paradigma, usuários buscam por documentos e recursos na Internet sem se importarem com o conhecimento explícito da localização do conteúdo. Como consequência, o endereço IP que previamente era utilizado como ponto de referência do provedor de dados, torna-se meramente um identificador efêmero do local onde o conteúdo está armazenado, resultando em implicações para a autenticação correta dos dados. Nesse contexto, a simples autenticação de um endereço IP não garante a autenticidade dos dados, uma vez que o servidor identificado por um dado endereço IP não é necessariamente o endereço do produtor do conteúdo. No contexto de redes orientadas à informação, existem propostas na literatura que possibilitam a autenticação dos dados utilizando somente o conteúdo propriamente dito, como a utilização de assinaturas digitais por bloco de dado e a construção de árvores de hash sobre os blocos de dados. A ideia principal dessas abordagens é atrelar uma informação do provedor original do conteúdo nos blocos de dados transportados, por exemplo, uma assinatura digital, possibilitando a autenticação direta dos dados com o provedor, independentemente do host onde o dado foi obtido. Apesar do mecanismo citado anteriormente possibilitar tal verificação, esse procedimento é muito oneroso do ponto de vista de processamento, especialmente quando o número de blocos é grande, tornando-o inviável de ser utilizado na prática. Este trabalho propõe um novo mecanismo de autenticação utilizando árvores de hash com o objetivo de prover a autenticação dos dados de forma eficiente e explícita com o provedor original e, também, de forma independente do host onde os dados foram obtidos. Nesta tese, propomos duas técnicas de autenticação de dados baseadas em árvores de hash, chamadas de skewed hash tree (SHT) e composite hash tree (CHT), para a autenticação de dados em redes orientadas à informação. Uma vez criadas, parte dos dados de autenticação é armazenada em um plano de segurança e uma outra parte permanece acoplada ao dado propriamente dito, possibilitando a verificação baseada no conteúdo e não no host de origem. Além disso, essa tese apresenta o modelo formal, a especificação e a implementação das duas técnicas de árvore de hash para autenticação dos dados em redes de conteúdo através de um plano de segurança. Por fim, esta tese detalha a instanciação do modelo de plano de segurança proposto em dois cenários de autenticação de dados: 1) redes Peer-to-Peer e 2) autenticação paralela de dados sobre o HTTPAbstract: Information security is responsible for protecting information against unauthorized access, use, modification or destruction. In order to protect such data against security attacks, many security protocols have been developed, for example, Internet Protocol Security (IPSec) and Transport Layer Security (TLS), providing mechanisms for data authentication, integrity and confidentiality for users. These protocols use the IP address as host identifier on the Internet, making it as a reference and identifier during the establishment of secure connections for data exchange between applications on the network. With the advent of the Web and the exponential increase in content consumption (e.g., video and audio), there is an evidence of a gradual migration of the predominant usage of the Internet, moving the emphasis on the connection between hosts to the content retrieval from the network, which paradigm is known as information-centric networking. In this paradigm, users look for documents and resources on the Internet without caring about the explicit knowledge of the location of the content. As a result, the IP address that was used previously as a reference point of a data provider, becomes merely an ephemeral identifier of where the content is stored, resulting in implications for the correct authentication data. In this context, the simple authentication of an IP address does not guarantee the authenticity of the data, because a hosting server identified by a given IP address is not necessarily the same one that is producing the requested content. In the context of information-oriented networks, some proposals in the literature proposes authentication mechanisms based on the content itself, for example, digital signatures over a data block or the usage of hash trees over data blocks. The main idea of these approaches is to add some information from the original provider in the transported data blocks, for example, a digital signature, enabling data authentication directly with the original provider, regardless of the host where the data was obtained. Although the mechanism mentioned previously allows for such verification, this procedure is very costly in terms of processing, especially when the number of blocks is large, making it unfeasible in practice. This thesis proposes a new authentication mechanism using hash trees in order to provide efficient data authentication and explicitly with the original provider, and also independently of the host where the data were obtained. We propose two techniques for data authentication based on hash trees, called skewed hash tree (SHT) and composite hash tree (CHT), for data authentication in information-oriented networks. Once created, part of the authentication data is stored in a security plane and another part remains attached to the data itself, allowing for the verification based on content and not on the source host. In addition, this thesis presents the formal model, specification and implementation of two hash tree techniques for data authentication in information-centric networks through a security plane. Finally, this thesis details the instantiation of the security plane model in two scenarios of data authentication: 1) Peer-to-Peer and 2) parallel data authentication over HTTPDoutoradoEngenharia de ComputaçãoDoutor em Engenharia Elétric

Towards Network Denial Of Service Resistant Protocols

Networked and distributed systems have introduced a new significant threat to the availability of data and services: network denial of service attacks. A well known example is the TCP SYN ooding. In general, any statefull handshake protocol is vulnerable to similar attacks. This paper examines the network denial of service in detail and surveys and compares different approaches towards preventing the attacks. As a conclusion, a number of protocol design principles are identified essential in designing network denial of service resistant protocols, and examples provided on applying the principles

TOWARDS NETWORK DENIAL OF SERVICE RESISTANT PROTOCOLS

Networked and distributed systems have introduced a new significant threat to the availability of data and services: network denial of service attacks. A well known example is the TCP SYN flooding. In general, any statefull handshake protocol is vulnerable to similar attacks. This paper examines the network denial of service in detail and surveys and compares different approaches towards preventing the attacks. As a conclusion, a number of protocol design principles are identified essential in designing network denial of service resistant protocols, and examples provided on applying the principles