A relevant feature of online social networks like Facebook is the scope for users to share external information from the web with their friends by sharing an URL. The phenomenon of sharing has bridged the web graph with the social network graph and the shared knowledge in ego networks has become a source for relevant information for an individual user, leading to the emergence of social search as a powerful tool for information retrieval. Consideration of the social context has become an essential factor in the process of ranking results in response to queries in social search engines. In this work, we present InfoSearch, a social search engine built over the Facebook platform, which lets users search for information based on what their friends have shared. We identify and implement three distinct ranking factors based on the number of mutual friends, social group membership, and time stamp of shared documents to rank results for user searches. We perform user studies based on the Facebook feeds of two authors to understand the impact of each ranking factor on the result for two queries.

Scalability issues make it time-consuming to estimate even simple characteristics of large scale, online networks, and the constantly evolving qualities of these networks make it challenging to capture a representative picture of a particular networks properties. Here we focus on the evolution of all triads (ties between three nodes) in a graph, as a method of studying change over time in large scale, online social networks. For three month snapshots, we examine, and predict, transitions among all sixteen triad types (i.e., triad census) in a sample of three years of Facebook wall-post interactions. We introduce a new sampling approach for examining triads in online graphs, based on ego-centric networks of random seeds. We examine tendencies in the data toward properties related to balance theory, including structural balance, clusterability, ranked clusters, transitivity, hierarchical clusters, and the presence of "forbidden" triads. In a time series analysis, we successfully predict the evolution over time in the wall post network dataset, with relatively low levels of error. The findings demonstrate the utility of our ego- centric, two-step, random seed sampling approach for studying large scale networks and predicting macroscopic graph properties, as well as the advantages of examining transitions in the complete triad census for an online network.

A TCPdump file captures not only packets but also various "properties" related to the live TCP sessions on the Internet. It is still an open problem to identify all the possible properties, if ever possible, and more importantly, which properties really matter for the consumers of this particular TCPdump file and how they are related to each other. However, it is quite clear that existing traffic replay tools, for the purpose of system evaluation, such as TCPreplay destroyed at least some of critical properties such as "ghost acknowledgment" (while the origin packet has never been delivered), which is a critical issue in conducting experimental evaluations for intrusion detection systems. In this paper, we present a software tool to transform an existing TCPdump file into another traffic file with different "properties". For instance, if the original traffic is being captured in a laboratory environment, the new file might "appear" to be captured in between US and Sweden. The transformation we have done here is "heuristically consistent" as there might be some hidden properties still being destroyed in the transformation process. One interesting application of our tool is to build long-term profiles to detect anomalous TCP attacks without really running the target application over the Internet. While, in this paper, we only focus on property-oriented traffic transformation, we have built and evaluated an interactive version of this tool, called TCPopera, to evaluate commercial intrusion prevention systems.

A practical decision system is developed for finding the adequate authentication level based on desirable security criteria and alternatives. Even though the notion of lightweight security is acknowledged, the process of determining when to use it instead of strong security is not well understood. The process of making such a decision can be very complex. By defining an overall security goal and a set of criteria with corresponding alternatives, the Analytic Hierarchy Process (AHP) is used to select the most suitable, preferred (and thus, adequate) authentication level, which is demonstrated by a realistic case study.

In recent years, technological advances have lead to a society with communication platforms like iPhone and Kinect Xbox that are able to inject sensing presence into online social networks (OSNs). Thus, it is possible to create large-scale opportunistic networks by integrating sensors, applications and social networks and this development could also promote innovative collaborative cyber security models. In this position paper, we discuss how social informatics will play a crucial role in trustworthy pervasive computing. With regard to security, our primary computing paradigm is still about processing information content only in order to make decisions. Given the availability of both digitized social informatics and sensor content, we now have the option to examine these sources simultaneously. We refer to this new era as the Social Computing Paradigm, and we argue that it could be particularly useful in conjunction with opportunistic sensing.

Given the wide deployment of IPSec/VPN (Virtual Private Networks) technology, there might be a redundancy in security protection in some configurations. Various commercial companies have replaced 802.11 security with IPSec/VPN to protect the wireless LAN (Local Area Network). How to do it in an efficient and lightweight way is a challenging research problem. This paper introduces a new lightweight identity authentication protocol, SOLA (Statistical One-bit Lightweight Authentication), for access control well suited for IEEE 802.11 networks with IP connections. This protocol prevents unauthorized access on a per packet basis. Since SOLA only adds one identity bit to each packet it will have a low impact on the network bandwidth and power consumption. The performance and efficiency of the SOLA protocol together with IEEE 802.11 is analyzed and evaluated via simulation.

In this paper we present the results of an experimental analysis of IPSec performance. IPSec serves as a security service to protect a communication session over unreliable networks using several cryptographic functions. The different IPSec features used to obtain confidentiality, authentication, replay protection, and integrity introduce performance costs brought about by the increased processing overhead. The performance parameters of interest are delay and throughput. However, there is a tradeoff between performance and security. The results of the performance tests indicate the vulnerability of a Denial-of-Service attack against a gateway running IPSec due to resource exhaustion.

This paper provides the contribution of mitigating a Denial-of-Service (DoS) attack via a developed hierarchical defense structure with proactive functionality. An important aspect is the tradeoff between performance and security. This novel hierarchical architecture is presented with lightweight authentication protocols acting as a classifier to deny access to harmful traffic. An empirical test of the proposed structure has been performed and results are reported which display the capability of the structure to filter and separate the attack traffic before reaching the target of an IPSec gateway. Thus, the filtering of traffic is performed without being the target itself for new resource exhaustion attacks. The considered IPSec environment is based on IPSec gateways for the low-end market, i.e., for small businesses or private networks.

A common question in social networking research is how edges form to produce social graphs with the common characteristics, including a power-law degree distribution and a small diameter. One common model for edge formation in synthetic networks is preferential attachment. We examine the edge formation process of one Online Social Network (OSN), Buzznet, and look for evidence for preferential attachment. To our surprise, we find that a form of "anti-preferential attachment" is common, in which high-degree nodes add edges to lowdegree nodes, perhaps as a means of self-promotion. We also find that nodes are most likely to reciprocate edges from low-degree nodes, limiting the extent to which anti-preferential attachment can succeed in boosting a high-degree node's in-degree.

Traditional security models based on distinguishing trusted from untrusted pieces of data and program behavior continue to face difficulties keeping up with attackers levels of sophistication and ingenuity. In this position paper, we present a novel computing paradigm for trustworthy computing whose application, operating system (OS) and architecture can leverage social trust to enhance the robustness and diversity of security mechanisms of any Internet-based computing environment. Our model would allow online social network (OSN) users to assign trust values to her friends in a privacy-preserving fashion and maintain a trust repository with trust values for objects like URLs, Email addresses, IP addresses and other pieces of data that can be consumed by a socially-aware OS, allowing for finegrained trust decisions that take into account user context and add diversity to host behavior. Our model also automatically infer trust values for people a user is not directly connected. In this paper we sketch the design of a socially-aware operating system kernel and identify several research challenges for this new paradigm.

The IEEE 802.11 wireless standard provides little support for secure access control. As a result, access control in IEEE 802.11 on a per packet basis requires a new and robust identity authentication protocol. The SOLA (Statistical One-Bit Lightweight Authentication) protocol is well suited in a wireless constrained environment because this protocol's communication overhead is extremely low: only one bit. Furthermore, SOLA fulfills the requirements of being secure, useful, cheap, and robust. The synchronization algorithm performs very well. SOLA also makes it easy to develop a framework to detect and respond to, for instance, denial-of-service attacks or an adversary who tries to guess the identity authentication bit for successive packets.

This informational draft describes the DPAC (Data Packet Access Control) framework, potentially under PANA, to efficiently control "data packets" to access the network. Instead of using potentially more expensive crypto-based mechanisms such as IPSec (layer 3) or IEEE 802.11i (layer 2), DPAC introduces the possibility of using and negotiating a range of light-weight per-data-packet source authentication methods to control the data packets from PANA Clients (PaC). In DPAC, each data packet sent from PaCs to Enhanced Point (EP) can be classified, with high probability, as either valid or invalid. Furthermore, under this framework, it is possible for EP and PAA to account reliably on the network usage of each PaC.

Given the wide and rapid depolyment of "visitor networks", how to authenticate the user and account the usage on the per-packet basis securely and yet efficiently is still a challenging problem. In this paper, we explore the tradoff between performance and security, and propose a per-data-packet authentication and access control called RBWA (Random Bit Window based Authentication). Deployed in the IP layer, RBWA can work with various underlying link layer specific mechanisms and network topologies. And comparing to IPSec, it dramatically reduces the overhead and power consumption by adding only a few bits to each packet. Furthermore, RBWA is strong against a suite of attacks such as replay attack, Denial-of-Service attack and spoofing etc. In particular, a robust anti-replay window scheme is developed to counter the svere packet reordering. The performance of RBWA is evaluated via the simulation.

Wiki systems, such as Wikipedia, provide a multitude of opportunities for large-scale online knowledge collaboration. Despite Wikipedia's successes with the open editing model, dissenting voices give rise to unreliable content due to conflicts amongst contributors. From our perspective, the conflict issue results from presenting the same knowledge to all readers, without regard for the importance of the underlying social context, which both reveals the bias of contributors and influences the knowledge perception of readers. Motivated by the insufficiency of the existing knowledge presentation model for Wiki systems, this paper presents TrustWiki, a new Wiki model which leverages social context, including social background and relationship information, to present readers with personalized and credible knowledge. Our experiment shows, with reliable social context information, TrustWiki can efficiently assign readers to their compatible editor community and present credible knowledge derived from that community. Although this new Wiki model focuses on reinforcing the neutrality policy of Wikipedia, it also casts light on the other content reliability problems in Wiki systems, such as vandalism and minority opinion suppression.

Wiki systems, such as Wikipedia, provide a multitude of opportunities for large-scale online knowledge collaboration. Despite Wikipedia's successes with the open editing model, dissenting voices give rise to unreliable content due to conflicts amongst contributors. Frequently modified controversial articles by dissent editors hardly present reliable knowledge. Some overheated controversial articles may be locked by Wikipedia administrators who might leave their own bias in the topic. It could undermine both the neutrality and freedom policies of Wikipedia. As Richard Rorty suggested "Take Care of Freedom and Truth Will Take Care of Itself"[1], we present a new open Wiki model in this paper, called TrustWiki, which bridge readers closer to the reliable information while allowing editors to freely contribute. From our perspective, the conflict issue results from presenting the same knowledge to all readers, without regard for the difference of readers and the revealing of the underlying social context, which both causes the bias of contributors and affects the knowledge perception of readers. TrustWiki differentiates two types of readers, "value adherents" who prefer compatible viewpoints and "truth diggers" who crave for the truth. It provides two different knowledge representation models to cater for both types of readers. Social context, including social background and relationship information, is embedded in both knowledge representations to present readers with personalized and credible knowledge. To our knowledge, this is the first paper on knowledge representation combining both psychological acceptance and truth reveal to meet the needs of different readers. Although this new Wiki model focuses on reducing conflicts and reinforcing the neutrality policy of Wikipedia, it also casts light on the other content reliability problems in Wiki systems, such as vandalism and minority opinion suppression.