Structured peer-to-peer overlay networks provide a sub-strate for the construction of large-scale, decentralized applications, including distributed storage, group com-munication, and content distribution. These overlays are highly resilient; they can route messages correctly even when a large fraction of the nodes crash or the network partitions. But current overlays are not secure; even a small fraction of malicious nodes can prevent correct message delivery throughout the overlay. This prob-lem is particularly serious in open peer-to-peer systems, where many diverse, autonomous parties without pre-existing trust relationships wish to pool their resources. This paper studies attacks aimed at preventing correct message delivery in structured peer-to-peer overlays and presents defenses to these attacks. We describe and eval-uate techniques that allow nodes to join the overlay, to maintain routing state, and to forward messages securely in the presence of malicious nodes. 1

Modern networking applications replicate data and services widely, leading to a need for location-independent routing---the ability to route queries to objects using names independent of the objects' physical locations. Two important properties of such a routing infrastructure are routing locality and rapid adaptation to arriving and departing nodes. We show how these two properties can be efficiently achieved for certain network topologies. To do this, we present a new distributed algorithm that can solve the nearest-neighbor problem for these networks. We describe our solution in the context of Tapestry, an overlay network infrastructure that employs techniques proposed by Plaxton et al. [24].

Mayday is an architecture that combines overlay networks with lightweight packet filtering to defend against denial of service attacks. The overlay nodes perform client authentication and protocol verification, and then relay the requests to a protected server. The server is protected from outside attack by simple packet filtering rules that can be efficiently deployed even in backbone routers. Mayday generalizes

Abstract — Over the Internet today, computing and communications environments are significantly more complex and chaotic than classical distributed systems, lacking any centralized organization or hierarchical control. There has been much interest in emerging Peer-to-Peer (P2P) network overlays because they provide a good substrate for creating large-scale data sharing, content distribution and application-level multicast applications. These P2P networks try to provide a long list of features such as: selection of nearby peers, redundant storage, efficient search/location of data items, data permanence or guarantees, hierarchical naming, trust and authentication, and, anonymity. P2P networks potentially offer an efficient routing architecture that is self-organizing, massively scalable, and robust in the wide-area, combining fault tolerance, load balancing and explicit notion of locality. In this paper, we present a survey and comparison of various Structured and Unstructured P2P networks. We categorize the various schemes into these two groups in the design spectrum and discuss the application-level network performance of each group.

Abstract. Peer-to-peer (p2p) networking technologies have gained popularity as a mechanism for users to share files without the need for centralized servers. A p2p network provides a scalable and fault-tolerant mechanism to locate nodes anywhere on a network without maintaining a large amount of routing state. This allows for a variety of applications beyond simple file sharing. Examples include multicast systems, anonymous communications systems, and web caches. We survey security issues that occur in the underlying p2p routing protocols, as well as fairness and trust issues that occur in file sharing and other p2p applications. We discuss how techniques, ranging from cryptography, to random network probing, to economic incentives, can be used to address these problems. 1

Decentralized Peer to Peer (P2P) networks offer both opportunities and threats. Its open and decentralized nature makes it extremely susceptible to malicious users spreading harmful content like viruses, trojans or, even just wasting valuable resources of the network. In order to minimize such threats, the use of community-based reputations as trust measurements is fast becoming a de-facto standard. The idea is to dynamically assign each peer a trust rating based on its performance in the network and store it at a suitable place. Any peer wishing to interact with another peer can make an informed decision based on such a rating.

In a Peer-To-Peer (P2P) system, autonomous computers pool their resources (e.g., les, storage, compute cycles) in order to inexpensively handle tasks that would normally require large costly servers. The scale of these systems, their \open nature", and the lack of centralized control pose dicult performance and security challenges. Much research has recently focused on tackling some of these challenges

Abstract. Distributed Hash Tables (DHTs) are very efficient distributed systems for routing, but at the same time vulnerable to disruptive nodes. Designers of such systems want them used in open networks, where an adversary can perform a sybil attack by introducing a large number of corrupt nodes in the network, considerably degrading its performance. We introduce a routing strategy that alleviates some of the effects of such an attack by making sure that lookups are performed using a diverse set of nodes. This ensures that at least some of the nodes queried are good, and hence the search makes forward progress. This strategy makes use of latent social information present in the introduction graph of the network.

Abstract — Overlay networks are widely used to deploy functionality at edge nodes without changing network routers. Each node in an overlay network maintains connections with a number of peers, forming a graph upon which a distributed application or service is implemented. In an “Eclipse ” attack, a set of malicious, colluding overlay nodes arranges for a correct node to peer only with members of the coalition. If successful, the attacker can mediate most or all communication to and from the victim. Furthermore, by supplying biased neighbor information during normal overlay maintenance, a modest number of malicious nodes can eclipse a large number of correct victim nodes. This paper studies the impact of Eclipse attacks on structured overlays and shows the limitations of known defenses. We then present the design, implementation, and evaluation of a new defense, in which nodes anonymously audit each other’s connectivity. The key observation is that a node that mounts an Eclipse attack must have a higher than average node degree. We show that enforcing a node degree limit by auditing is an effective defense against Eclipse attacks. Furthermore, unlike most existing defenses, our defense leaves flexibility in the selection of neighboring nodes, thus permitting important overlay optimizations like proximity neighbor selection (PNS). I.

In this paper, we show that two peer-to-peer systems, Pastry [13] and Tapestry [17] can be made tolerant to certain classes of failures and a limited class of attacks. These systems are said to operate properly if they can find the closest node matching a requested ID.