Abstract

Research to date on the examination process for postgraduate research theses has focused largely on the deconstruction of examiners' reports. This article reports on a study of the processes that experienced examiners go through, and the judgements they make before writing their reports. A sample of 30 experienced examiners (defined as having examined the equivalent of at least five research theses over the last five years), from a range of disciplines in five universities was interviewed. Clear trends emerged with regard ...

Abstract

An ad hoc network is a collection of wireless mobile hosts forming a temporary network without the aid of any established infrastructure or centralized administration. In such an environment, it may be necessary for one mobile host to enlist the aid of other hosts in forwarding a packet to its destination, due to the limited range of each mobile host’s wireless transmissions. This paper presents a protocol for routing in ad hoc networks that uses dynamic source routing . The protocol ...

Abstract

Real world recommendation systems, personalized mobile search, and online city guides could all benefit from data on personal place preferences. However, collecting explicit rating data of locations as users travel from place to place is impractical. This paper investigates the relationship between explicit place ratings and implicit aspects of travel behavior such as visit frequency and travel time. We conducted a four-week study with 16 participants using a novel sensor-based experience sampling tool, called My Experience (Me), which we developed for ...

Abstract

The credibility of mobile ad hoc network simulations depends on accurate characterisations of user behaviour, e.g., mobility and application usage. If simulated nodes communicate at different rates to real nodes, or move in an unrealistic fashion, this may have a large impact on the network protocols being simulated and tested. Many future mobile network protocols, however, may also depend on future mobile applications. Different applications may be used at different rates or in different manners. But how can we determine realistic ...

Abstract

In this paper we present constructive algorithms for generating realistic synthetic ego networks (one of the most important representations of human social networks). These algorithms are based on ego network models derived in the anthropology literature, which describe the key structural properties of ego networks, and the properties of the social relationships between individuals. The main area we consider for applying these algorithms is the study of social networking environments currently under discussion in the research community. In particular, we focus ...

Abstract

Abstract movement models, such as Random Waypoint, do not capture reliably the properties of movement in the real life scenarios. We present and analyse a movement model for delay-tolerant network simulations that is able to produce inter-contact time and contact time distributions that follow closely the ones found in the traces from the real-world measurement experiments. We validate the movement model using the ONE simulator. ...

Abstract

In 1980 Martin Hellman described a cryptanalytic time-memory trade-off which reduces the time of cryptanalysis by using precalculated data stored in memory. This technique was improved by Rivest before 1982 with the introduction of distinguished points which drastically reduces the number of memory lookups during cryptanalysis. This improved technique has been studied extensively but no new optimisations have been published ever since. We propose a new way of precalculating the data which reduces by two the number of calculations needed during ...

Abstract

In this paper trade-offs among certain computational factors in hash coding are analyzed. The paradigm problem considered is that of testing a series of messages one-by-one for membership in a given set of messages. Two new hash-coding methods are examined and compared with a particular conventional hash-coding method. The computational factors considered are the size of the hash area (space), the time required to identify a message as a nonmember of the given set (reject time), and an allowable error frequency. ...

Abstract

TrackMeNot (TMN) is a Firefox browser extension designed to achieve privacy in Web search by obfuscating users’ queries within a stream of programmatically generated decoys. Since August 2006, when the initial version of TMN was made publicly available free of charge, there have been over 350,000 downloads. TMN protects Web users against data profiling by simulating HTTP search requests to search engines with queries extracted from the Web. In an attempt to mimic users’ search behavior, this basic functionality is augmented with several technical mechanisms: dynamic query lists ...

Abstract

In summary, Onion Routing is a traffic analysis resistant infrastructure that is easily accessible, has low overhead, can protect a wide variety of applications, and is flexible enough to adapt to various network environments and security needs. The system is highly extensible, allowing for additional symmetric cryptographic algorithms, proxies, or routing algorithms with only minor modifications to the existing code base. Instructions for accessing the Onion Routing network can be found on our Web page (www.onion-router.net) along with additional background and ...

Abstract

This paper proposes Habit, an efficient multi-layered approach to content dissemination in Delay Tolerant Networks (DTN) that leverages information about nodes' colocation (physical layer) and their social network (application layer). More precisely, the regularity of users' colocation is learned based on historical colocation observations; also, the users' social network (or 'network of interest') is dynamically propagated during periods of colocation; finally, these distinct pieces of information are locally combined and used to compute the paths that content should follow, in a ...

Abstract

A delay-tolerant network is a mobile ad hoc network where the message dissemination is based on the store-carry-and-forward principle. This principle raises new aspects of the privacy problem. In particular, an attacker can build a user profile and trace the nodes based on this profile even if the message exchange protocol provides anonymity. In this paper, an attacker model is presented and some proposed attackers are implemented. We analyze the efficiency of both the attacks and the proposed defense mechanism, called ...

Abstract

Several techniques to improve anonymity have been proposed in the literature. They rely basically on multicast or on onion routing to thwart global attackers or local attackers respectively. None of the techniques provide a combined solution due to the incompatibility between the two components, as we show in this paper. We propose novel packet coding techniques that make the combination possible, thus integrating the advantages in a more complete and robust solution ...

Abstract

Opportunistic networks have been the study of much research — in particular on making end-to-end routing efficient. Users' privacy concerns, however, have not been the subject of much research. What privacy concerns might opportunistic network users have? Is it possible to build opportunistic networks that can mitigate users' privacy concerns while maintaining routing performance? Our work-to-date has tackled the problem of creating privacy-preserving routing protocols, with less emphasis on discovering users' actual privacy concerns. We summarise our current results, and describe a ...

Abstract

Peer-to-peer and other decentralized,distributed systems are known to be particularly vulnerable to sybil attacks . In a sybil attack,a malicious user obtains multiple fake identities and pretends to be multiple, distinct nodes in the system. By controlling a large fraction of the nodes in the system,the malicious user is able to "out vote" the honest users in collaborative tasks such as Byzantine failure defenses. This paper presents SybilGuard , a novel protocol for limiting the corruptive influences of sybil ...

Abstract

Mobile ad hoc networks (MANETs) are proposed as an extremely flexible technology for establishing wireless communications. In comparison with fixed networks or traditional mobile cellular networks, MANETs introduce some new security issues. Especially, the routing security is the most important and complicated one. In this work, we propose a two-tier authentication mechanism for MANETs. The first tier, based on a hash function and the concept of MAC, provides fast message verification and group identification. The second tier, based on secret sharing ...

Abstract

In Sybil attack, an attacker acquires multiple identities and uses them simultaneously or one by one to attack various operation of the network. Such attacks pose a serious threat to the security of self-organized networks like mobile ad-hoc networks (MANETs) that require unique and unchangeable identity per node for detecting routing misbehavior and reliable computation of node's reputation. The purpose of this paper is to analyze the effectiveness of current authentication mechanism for MANETs in coping with the Sybil attack, the ...

Abstract

Flooding attack is a novel and powerful attack against on-demand ad hoc routing protocols. At present, FAP (flooding attack prevention) is the single scheme proposed to resist such attack. This paper analyses the security hole of FAP, and presents a new and simpler solution, AMTT (avoiding mistaken transmission table) scheme. In this scheme, legal nodes can distinguish illegal nodes and refuse to forward packages for them, so flooding attack can be defended. Through analysis, AMTT shows it can resist flooding attack ...

Abstract

Malicious data packet flooding attacks interfere with services of a victim node such as laptop computer, cellular phone, etc. in wireless ad hoc networks. The victim node is hard to distinguish traffics performing data packet flooding attacks from normal burst traffics. Hence, this paper proposes a period-based scheme so as to prevent from malicious data packet flooding attacks with enhancing the throughput of burst traffics. The simulation results show that the proposed scheme enhances the throughput of burst traffics. ...

Abstract

Probabilistic routing protocols in Delay Tolerant Networks (DTN) make use of the mobility history in its prediction when making a forwarding decision. However, the predictive property can expose DTN to more advanced security threats. One security threat is enhanced flooding attack which can be more penetrative if properly planned as malicious nodes have prior knowledge of their victims. However, through the investigation of various flooding techniques, we propose to capitalize this very probabilistic feature to confine and mitigate flooding attacks through ...

Abstract

Mobile ad hoc network (MANET) is particularly vulnerable to flooding attacks. To evade being identified, attackers usually recruit multiple accomplices to dilute attack traffic density of each attack source, and use the address spoofing technique to challenge attack tracing. In this paper, we present a detailed investigation of the flooding attack in MANET. Further, we design two flow based detection features, and apply the cumulative sum algorithm on them to effectively and accurately detect such attack. ...

Abstract

In this work, we study robustness of DTN routing in the absence of authentication. We identify conditions for an attack to be effective and present an attack based on a combination of targeted flooding and acknowledgement counterfeiting that is highly effective even with only a small number of attackers. Simulation results show that delivery ratio decrease by 30% to 50% using only 2 attackers for the two mobility patterns studied (Haggle and DieselNet). We observe that minimum hop count for packet ...

Abstract

Disruption-Tolerant Networks (DTNs) deliver data in network environments composed of intermittently connected nodes. Just as in traditional networks, malicious nodes within a DTN may attempt to delay or destroy data in transit to its destination. Such attacks include dropping data, flooding the network with extra messages, corrupting routing tables, and counterfeiting network acknowledgments. Many existing methods for securing routing protocols require authentication supported by mechanisms such as a public key infrastructure, which is difficult to deploy and operate in a DTN, ...

Abstract

In this article we present the current state of the art in IP traceback. The rising threat of cyber attacks, especially DDoS, makes the IP traceback problem very relevant to today's Internet security. Each approach is evaluated in terms of its pros and cons. We also relate each approach to practical deployment issues on the existing Internet infrastructure. The functionality of each approach is discussed in detail and then evaluated. We conclude with a discussion on some legal implications of IP ...

Abstract

Flooding-type Denial-of-Service (DoS) and Distributed DoS (DDoS) attacks can cause serious problems in mobile multi-hop networks due to its limited network/host resources. Attacker traceback is a promising solution to take a proper countermeasure near attack origins, for forensics and to discourage attackers from launching the attacks. However, attacker traceback in mobile multi-hop networks is a challenging problem. Existing IP traceback schemes developed for the fixed networks cannot be directly applied to mobile multi-hop networks due to the peculiar characteristics of the ...

Abstract

In this paper, we propose countermeasures to mitigate damage caused by spoofing attacks in Delay-Tolerant Networks (DTNs). In our model, an attacker spoofs someone else's address (the victim's) to absorb packets from the network intended for that victim. Address spoofing is arguably a very severe attack in DTNs, compared to other known attacks, such as dropping packets. Without a Public Key Infrastructure in DTNs, providing protection against this attack is challenging. We propose SPREAD (countermeasure against SPoofing by REplica ADjustment), a ...

Abstract

Opportunistic routing protocols can enable message delivery in disconnected networks of mobile devices. To conserve energy in mobile environments, such routing protocols must minimise unnecessary message-forwarding. This paper presents an opportunistic routing protocol that leverages social role information. We compute node roles from a social network graph to identify nodes with similar contact relationships, and use these roles to determine routing decisions. By using pre-existing social network information, such as online social network friends, to determine roles, we show that our ...

Abstract

Large-scale peer-to-peer systems face security threats from faulty or hostile remote computing elements. To resist these threats, many such systems employ redundancy. However, if a single faulty entity can present multiple identities, it can control a substantial fraction of the system, thereby undermining this redundancy. One approach to preventing these "Sybil attacks" is to have a trusted agency certify identities. This paper shows that, without a logically centralized authority, Sybil attacks are always possible except under extreme and unrealistic assumptions of ...

Abstract

Mobility is often a problem for providing security services in ad hoc networks. In this paper, we show that mobility can be used to enhance security. Specifically, we show that nodes that passively monitor traffic in the network can detect a Sybil attacker that uses a number of network identities simultaneously. We show through simulation that this detection can be done by a single node, or that multiple trusted nodes can join to improve the accuracy of detection. We then show ...

Abstract

A DDoS (distributed denial-of-service) attack is a distributed, large-scale attempt by malicious users to flood the victim network with an enormous number of packets. This exhausts the victim network of resources such as bandwidth, computing power, etc. The victim is unable to provide services to its legitimate clients and network performance is greatly deteriorated. There are many proposed methods in the literature which aim to alleviate this problem; such as hop-count filtering, rate-limiting and statistical filtering. However, most of these solutions ...

Abstract

An opportunistic network is a type of challenged network that has attracted a great deal of attention in recent years. While a number of schemes have been proposed to facilitate data dissemination in opportunistic networks, there is an implicit assumption that each participating peer behaves collaboratively. Consequently, these schemes may be vulnerable if there are uncooperative or malicious peers in the network. In this study, we identify five types of non-collaborative behavior, namely free rider, black hole, supernova, hypernova, and wormhole ...

Abstract

Distributed denial-of-service (DDoS) is a rapidly growing problem. The multitude and variety of both the attacks and the defense approaches is overwhelming. This paper presents two taxonomies for classifying attacks and defenses, and thus provides researchers with a better understanding of the problem and the current solution space. The attack classification criteria was selected to highlight commonalities and important features of attack strategies, that define challenges and dictate the design of countermeasures. The defense taxonomy classifies the body of existing DDoS ...

Abstract

In this paper we introduce LENS, a novel spam protection system based on the recipient's social network, which allows correspondence within the social circle to directly pass to the mailbox and further mitigates spam beyond social circles. The key idea in LENS is to select legitimate and authentic users, called Gatekeepers (GKs), from outside the recipients social circle and within pre-defined social distances. Unless a GK vouches for the emails of potential senders from outside the social circle of a particular ...

Abstract

In a turn-based networked multiplayer computer game, it is possible to cheat by delaying the announcement of one’s action for a turn until one has received messages from all the other players. This look-ahead cheating can be prevented with a lockstep protocol, which requires that the player first announces a commitment to an action and later on the action itself, which can be compared with the earlier announced commitment. However, because the lockstep protocol requires separate transmissions for the commitment and ...

Abstract

Online social networks (OSNs) are extremely popular among Internet users. Unfortunately, in the wrong hands, they are also effective tools for executing spam campaigns. In this paper, we present an online spam filtering system that can be deployed as a component of the OSN platform to in- spect messages generated by users in real-time. We propose to reconstruct spam messages into campaigns for classifica- tion rather than examine them individually. Although cam- paign identification has been used for offline spam analysis, we apply this technique to aid the online spam ...

Abstract

Making new connections according to personal preferences is a crucial service in mobile social networking, where the initiating user can find matching users within physical proximity of him/her. In existing systems for such services, usually all the users directly publish their complete profiles for others to search. However, in many applications, the users' personal profiles may contain sensitive information that they do not want to make public. In this paper, we propose FindU, the first privacy-preserving personal profile matching schemes for ...

Abstract

This paper addresses the problem of identifying the top-k information hubs in a social network. Identifying top-k information hubs is crucial for many applications such as advertising in social networks where advertisers are interested in identifying hubs to whom free samples can be given. Existing solutions are centralized and require time stamped information about pair-wise user interactions and can only be used by social network owners as only they have access to such data. Existing distributed and privacy preserving algorithms suffer ...

Note (first note only)

From Abstract: Our method can identify hubs without requiring a central entity to access the complete friendship graph.

From Introduction (I.B): However, centralized computation of top-k information hubs is mostly unrealistic for parties such as advertisers because online social networking companies are reluctant to share their interaction or friendship graphs due to privacy concerns, regulations [1] and usage limitations in the terms of service [3].

Abstract

Mobile social networks extend social networks in the cyberspace into the real world by allowing mobile users to discover and interact with existing and potential friends who happen to be in their physical vicinity. Despite their promise to enable many exciting applications, serious security and privacy concerns have hindered wide adoption of these networks. To address these concerns, in this paper we develop novel techniques and protocols to compute social proximity between two users to discover potential friends, which is an ...

Abstract

The presence of multimodal sensors on current mobile phones enables a broad range of novel mobile applications. Environmental and user-centric sensor data of unprecedented quantity and quality can be captured and reported by a possible user base of billions of mobile phone subscribers worldwide. The strong focus on the collection of detailed sensor data may however com- promise user privacy in various regards, e.g., by tracking a user’s current location. In this survey, we identify the sensing modalities used in current participatory sensing applications, and assess the threats ...

Abstract

Receiver-location privacy is an important security requirement in privacy-preserving Vehicular Ad hoc Networks (VANETs), yet the unavailable receiver's location information makes many existing packet forwarding protocols inefficient in VANETs. To tackle this challenging issue, in this paper, we propose an efficient social-tier-assisted packet forwarding protocol, called STAP, for achieving receiver-location privacy preservation in VANETs. Specifically, by observing the phenomena that vehicles often visit some social spots, such as well-traversed shopping malls and busy intersections in a city environment, we deploy storage-rich ...

Note (first note only)

From Abstract: by observing the phenomena that vehicles often visit some social spots, such as well-traversed shopping malls and busy intersections in a city environment, we deploy storage-rich Roadside Units (RSUs) at social spots and form a virtual social tier with them. Then, without knowing the receiver’s exact location information, a packet can be first forwarded and disseminated in the social tier. Later, once the receiver visits one of social spots, it can successfully receive the packet.

Abstract

The United States Department of Defense designed the Global Positioning System (GPS) in the early 1970s to track the position of military troops and equipment.1 GPS consists of a network of satellites that transmit radio signals to Earth, where a radio receiver then triangulates its own position based upon the readings from the satellites.2 Following an airline mishap in the 1980s, GPS became available for civilian use and safety purposes due to its superior navigation capability. ...

Abstract

We present the design, implementation, and evaluation of Caché, a system that offers location privacy for certain classes of location-based applications. The core idea in Caché is to periodically pre-fetch potentially useful location-enhanced content well in advance. Applications then retrieve content from a local cache on the mobile device when it is needed. This approach allows an end-user to make use of location-enhanced content while only revealing to third-party content providers a large geographic region rather than a precise location. In ...

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From Introduction: A key challenge to widespread adoption of location-based services, however, is privacy [19]. One problem is the per- ception of privacy: people have expressed many concerns about being tracked by friends and by third parties. Lo- cation privacy concerns also tend to attract negative media coverage, further hindering the spread of location-based ser- vices. Another problem is actual privacy: end-users may be unaware of the privacy implications of location-based tech- nologies [3, 4], and end up unintentionally sharing more in- formation than they realize.

Abstract

Laboratory-based mobile wireless testbeds such as MeshTest and the CMU Wireless Emulator are powerful platforms that allow users to perform controlled, repeatable, mobile wireless experiments in the lab. Unfortunately such systems can only accommodate 10-15 nodes in an experiment. We have designed and built a scalable wireless testbed that uses software virtualization and live migration to facilitate experiments involving intermittently connected networks with many multiples of the number of physical nodes available on such a testbed. In this paper, we share ...

Abstract

An old joke tells of a driver, returning home from a party where he had one drink too many, who hears a warning over the radio about a car careening down the wrong side of the highway. “A car?” he wondered aloud, “There are lots of cars on the wrong side of the road!” I am afraid that driver is us, the computing-research community. What I’m referring to is the way we go about publishing our research results. As far as I know, we are the only scientific community that considers conference publication ...

Abstract

Security- and privacy-related tools often feature graphical (or in some cases textual or audio) indicators designed to assist users in protecting their security or privacy. But a growing body of literature has found the effectiveness of many of these indicators to be rather disappointing. ...

Abstract

The near future could take cooperation among mobile Internet users to a new level of sharing wireless access and interacting without any network infrastructure at all. The basic technologies exist — all we need is a bit of altruistic behavior and the right mobile apps penetrating the market at scale. Here, the author looks at an individual serving others as an ISP. ...

Abstract

Social computing has led to an explosion of research in understanding users, and it has the potential to similarly revolutionize systems research. However, the number of papers designing and building new sociotechnical systems has not kept pace. We analyze challenges facing social computing systems research, ranging from misaligned methodological incentives, evaluation expectations, double standards, and relevance compared to industry. We suggest improvements for the community to consider so that we can chart the future of our field. ...

Note (first note only)

Get Out of the Snow! No Snowball Sampling: ... snowball sampling is inevitable in social systems. ... random sampling can be an impossible standard for social computing research. ... Finally, snowball sampling is another form of convenience sampling, and convenience sampling is common practice across CHI, social sciences and systems research.

Novelty: Between A Rock and A Hard Science: When Studiers review this work, even well-intentioned ones may then fall into the Fatal Flaw Fallacy [27]: rejecting a systems research paper because

Abstract

Delay-tolerant Networking (DTN) enables communication in sparse mobile ad-hoc networks and other challenged environments where traditional networking fails and new routing and application protocols are required. Past experience with DTN routing and application protocols has shown that their performance is highly dependent on the underlying mobility and node characteristics. Evaluating DTN protocols across many scenarios requires suitable simulation tools. This paper presents the Opportunistic Networking Environment (ONE) simulator specifically designed for evaluating DTN routing and application protocols. It allows users to ...

Note (first note only)

http://www.netlab.tkk.fi/tutkimus/dtn/theone/ - "If you have used the ONE simulator in your research, please use the SIMUTools paper ([PDF] [BibTeX]) as the reference."

Abstract

When applying delay-tolerant networking concepts to communication in mobile ad-hoc networks formed between mobile users, a general assumption is that users are willing to share own resources to support communication between others. However, we cannot assume that all users are altruistic in their behavior; instead, we have to deal with users who only make a limited or no contribution to the mobile community. Nodes not participating in communication only reduce the effective node density, but do not consume resources. Others act ...

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cf. SeSoc (SSNR: -40%).

Abstract: We introduce two types of selfish nodes and evaluate their impact on message delivery performance for different routing protocols by means of simulation in different synthetic mobility models and with real-world traces. We find that their impact can be surprisingly low in our scenarios, suggesting that DTN communication can be quite robust against selfishness and that controlled non-cooperative behavior may be a suitable way to overcome resource limitations, such as battery depletion.

Abstract

Opportunistic networks use human mobility and consequent wireless contacts between mobile devices to disseminate data in a peer-to-peer manner. Designing appropriate algorithms and protocols for such networks is challenging as it requires understanding patterns of (1) mobility (who meets whom), (2) social relations (who knows whom) and (3), communication (who communicates with whom). To date, apart from few small test setups, there are no operational opportunistic networks where measurements could reveal the complex correlation of these features of human relationships. Hence, ...

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Abstract: Stumbl is a Facebook application that provides participating users with a user-friendly interface to report their daily face-to-face meetings with other Facebook friends. It also logs user interactions on Facebook (e.g. comments, wall posts, likes). This way the contact graph, social graph, and activity graphs for the same set of users could be compared and analyzed.