Mitigating Distributed Denial of Service Attacks in an Anonymous Routing Environment: Client Puzzles and Tor

Online intelligence operations use the Internet to gather information on the activities of U.S. adversaries. The security of these operations is paramount, and one way to avoid being linked to the Department of Defense (DoD) is to use anonymous communication systems. One such system, Tor, makes interactive TCP services anonymous. Tor uses the Transport Layer Security (TLS) protocol and is thus vulnerable to a distributed denial-of-service (DDoS) attack that can significantly delay data traversing the Tor network. This research uses client puzzles to mitigate TLS DDoS attacks. A novel puzzle protocol, the Memoryless Puzzle Protocol (MPP), is conceived, implemented, and analyzed for anonymity and DDoS vulnerabilities. Consequently, four new secondary DDoS and anonymity attacks are identified and defenses are proposed. Furthermore, analysis of the MPP identified and resolved two important shortcomings of the generalized client puzzle technique. Attacks that normally induce victim CPU utilization rates of 80-100% are reduced to below 70%. Also, the puzzle implementation allows for user-data latency to be reduced by close to 50% during a large-scale attack .Finally, experimental results show successful mitigation can occur without sending a puzzle to every requesting client. By adjusting the maximum puzzle strength, CPU utilization can be capped at 70% even when an arbitrary client has only a 30% chance of receiving a puzzle

Obituary: Arthur Cruickshank 1932 - 2011. A native Gondwanan, who studied the former continent's fossil tetrapods

Dr Arthur Richard Ivor Cruickshank died on 4th December 2011, aged 79, in the Borders General Hospital, Melrose, Scotland. Arthur Cruickshank was part of the post-war generation of palaeontologists who laid the foundations on which today’s researchers build. Appropriately for someone from an expatriate Scots family living in Kenya, much of his work was on the extinct reptiles of the great southern palaeocontinent of Gondwana

Motivations, concerns and selection biases when posting preprints: A survey of bioRxiv authors

Since 2013, the usage of preprints as a means of sharing research in biology has rapidly grown, in particular via the preprint server bioRxiv. Recent studies have found that journal articles that were previously posted to bioRxiv received a higher number of citations or mentions/shares on other online platforms compared to articles in the same journals that were not posted. However, the exact causal mechanism for this effect has not been established, and may in part be related to authors' biases in the selection of articles that are chosen to be posted as preprints. We aimed to investigate this mechanism by conducting a mixed-methods survey of 1,444 authors of bioRxiv preprints, to investigate the reasons that they post or do not post certain articles as preprints, and to make comparisons between articles they choose to post and not post as preprints. We find that authors are most strongly motivated to post preprints to increase awareness of their work and increase the speed of its dissemination; conversely, the strongest reasons for not posting preprints centre around a lack of awareness of preprints and reluctance to publicly post work that has not undergone a peer review process. We additionally find evidence that authors do not consider quality, novelty or significance when posting or not posting research as preprints, however, authors retain an expectation that articles they post as preprints will receive more citations or be shared more widely online than articles not posted.Seit 2013 hat die Nutzung von Preprints als Mittel zur Verbreitung von Forschungsergebnissen in der Biologie stark zugenommen, insbesondere über den Preprint-Server bioRxiv. Jüngste Studien haben ergeben, dass Zeitschriftenartikel, die zuvor auf bioRxiv veröffentlicht wurden, auf anderen Online-Plattformen häufiger zitiert oder erwähnt/geteilt wurden als Artikel derselben Zeitschriften, die nicht veröffentlicht wurden. Der genaue kausale Mechanismus für diesen Effekt ist jedoch nicht geklärt und könnte zum Teil mit der Voreingenommenheit der Autor*innen bei der Auswahl der Artikel, die als Preprints veröffentlicht werden, zusammenhängen. Die Autor*innen wollten diesen Mechanismus untersuchen, indem sie eine mixed-methods-Umfrage unter 1.444 Autor*innen von bioRxiv-Preprints durchführten, um die Gründe zu untersuchen, aus denen sie bestimmte Artikel als Preprints veröffentlichen oder nicht veröffentlichen, und um Vergleiche zwischen Artikeln anzustellen, die sie als Preprints veröffentlichen oder nicht veröffentlichen. Sie stellen fest, dass Autor*innen am stärksten motiviert sind, Preprints zu veröffentlichen, um den Bekanntheitsgrad ihrer Arbeit zu erhöhen und deren Verbreitung zu beschleunigen. Umgekehrt liegen die stärksten Gründe für die Nichtveröffentlichung von Preprints in der mangelnden Bekanntheit von Preprints und der Abneigung, eine Arbeit zu veröffentlichen, die keinen Peer-Review-Prozess durchlaufen hat