XP is a lightweight process that provides principles for guiding projects and relies on the participants for its success. However, despite these guidelines, projects can be unsuccessful. We have previously identified that participants' levels of "buy-in" into the ethos of the methodology is a significant determinant of project success. This paper investigates how team formation influences buy-in and how buy-in, in turn, effects success, learning and working attitude within an academic environment. The empirical study shows that teams comprised of people with similar understandings of, and attitudes towards, the process tend to have a higher level of buy-in and, as a result, exceed their expected performance potential.

Searching and organization of peers are fundamental challenges in P2P networks. Unstructured networks, such as Gnutella, inefficiently use broadcast searches and random neighbors. Structured networks are similarly inefficient, as they generally rely on globally unique identifiers (GUIDs) which are assigned irrespective of content, which prevents fuzzy semantic searches. In both types of network search, neighbors establish trust between themselves, regardless of whether or not their content is likely to satisfy searches. We present the idea of using context-based profiles to describe peers. This enables self-organizing clusters of similar peers. A profile represents a peer's expertise based on content and responsiveness. By refining the search process using these profiles, more efficient directed searches are possible. Moreover, expertise provides a basis for trust establishment.

Trading privacy for trust thanks to the linkage of pseudonyms has been proposed to mitigate the inherent conflict between trust and privacy. This necessitates fusionym, that is, the calculation of a unique trust value supposed to reflect the overall trustworthiness brought by the set of linked pseudonyms. In fact, some pieces of evidence may overlap and be overcounted, leading to an incorrect trust value. In this approach, self-recommendations are possible during the privacy/trust trade. However, this means that Sybil attacks, where thousands of virtual identities belonging to the same real-world entity recommend each other, are potentially easier to carry out, as self-recommendations are an integral part of the attack. In this paper, trust transfer is used to achieve safe fusionym and protect against Sybil attacks when pieces of evidence are limited to direct observations and recommendations based on the count of event outcomes. Trust transfer implies that recommendations move some of the trustworthiness of the recommending entity to the trustworthiness of the trustee. It is demonstrated and tailored to email anti-spam settings.

Bankable Postage (BP) has been proposed as a mechanism to attack the underlying techico-economic reasons for spamming. However, BP is costly to legitimate users and threatens to be undermined by spoofing attacks. In this paper we show how to use the Claim Tool Kit to defeat these attacks and propose a collaborative recommendation technique to reduce the number of BPs required by legitimate users. Known, trustworthy senders can introduce new senders to their contacts free of charge. BPs are only necessary when no mutually trustworthy third party is able to introduce sender and receiver. We show that this can significantly reduce the number of BPs required by legitimate users, in the absence of attackers. However, collaboration introduces its own set of attacks. Depending on the search scheme, an empirical evaluation on a real-world network of email users indicates that random pleasing attacks and network topology engineered attacks, where the most important email users are pleased; significantly reduce the spammer attack cost.

The state of the art sees content-based filters tending towards collaborative filters, whereby email is filtered at the MTA with users feeding information back about false positives and negatives. While this improves the ability of the filter to track concept drift in spam over time, such approaches make assumptions implicit in centralised spam filtering, such as that all users consider the same email to be spam. In this paper, we detail and analyse these assumptions and describe how they affect spam filtering. We present an architecture for personalised, collaborative spam filtering and describe the design and implementation of proof-of-concept, peer-to-peer, signature-based system based on the architecture. The evaluation is based on real-world users employing the system as their spam-filtering tool. Preliminary analysis of the results indicates that the implementation is accurate and efficient.

Agile processes such as XP (extreme programming) have been recognised for their potential benefits of improving software. During adoption of the XP process, teams can misapply the XP principles by following them verbatim, ignoring the context in which they are applied. In this paper we document our experiences where naive applications of XP principles were altered in recognition of context. We detail our observations of how teams "looked behind" the rules and began fitting XP to the problem rather than attempting to fit the problem to XP. We conclude by reflectively focusing on how this transformation occurred and suggest that it is buying into the XP ethos that drives this change of perspective on the XP process and principles.