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Adopting the criminal event perspective, we explore how online fraudsters make use of urgency cues in their interactions with potential victims throughout the progression of an online nonpayment fr...

Focusing on two of the most common deceptive strategies employed by fraudsters, we assess which type of cue—politeness or urgency—is more likely to result in an email fraud attempt. We also examine whether these cues are mutually exclusive and consistent throughout the progression of a fraud attempt. To answer our research questions, we posted “for-sale” advertisements on classified-advertisement websites and interacted with fraudsters who responded to our advertisements. Findings reveal that fraud attempts are more likely to follow probe emails that include cues of urgency than cues of politeness. Moreover, although the majority of fraudsters’ probe emails include deceptive cues of either politeness or urgency, the majority of subsequent emails include deceptive cues of both politeness and urgency.

This chapter focuses on the taxonomy of scam emails collected from various sources and investigates long-term trends in scam emails. We first describe a large-scale compendium of scam emails collected from various sources, and then present an analysis regarding what kind of scams exist, what their structures are, and how they are related to each other. We then describe a machine learning classifier built based upon the taxonomy analysis, and use it to cluster scam emails into major scam categories. Then an analysis of different trends from each scam category is presented. Our analysis shows a clear trend that spam-like non-targeted scams are decreasing continuously while targeted scams with specific victims have been getting more prevalent over the last 10 years.

In this chapter, a systematic empirical study of the online rental scams on Craigslist and its ecosystem is presented. By developing several effective detection techniques, several major rental scam campaigns on Craigslist were identified. In addition, a system was built to automatically contact suspected rental scammers, which enabled us to understand what support infrastructure they used and how they were monetizing their postings.

This chapter focuses on a common type of consumer-facing scam referred to as the sales scam, focusing on the scam’s occurrence on Craigslist, one of the most popular online market websites, with over 60 million monthly visitors in the U.S. alone. In spite of the prevalence of scams on Craigslist, the community’s understanding of these is still very much lacking, and in this chapter and the two chapters following it, we present in-depth measurement studies of such scam activities. These measurement studies aim to better understand the underground economy of scams on Craigslist, and seek effective intervention points. In particular, we seek to address questions such “Where are scammers located?”, “How do scam factories operate?”, and “How effective are current defenses?”. While the answers certainly do not translate to all types of scams—not even all those on Craigslist—they provide interesting insights into the problem and show how to design metrics to assess its nature.

DDoS-for-hire services, also known as booters, have commoditized DDoS attacks and enabled abusive subscribers of these services to cheaply extort, harass and intimidate businesses and people by taking them offline. However, due to the underground nature of these booters, little is known about their underlying technical and business structure. In this paper, we empirically measure many facets of their technical and payment infrastructure. We also perform an analysis of leaked and scraped data from three major booters---Asylum Stresser, Lizard Stresser and VDO---which provides us with an in-depth view of their customers and victims. Finally, we conduct a large-scale payment intervention in collaboration with PayPal and evaluate its effectiveness as a deterrent to their operations. Based on our analysis, we show that these booters are responsible for hundreds of thousands of DDoS attacks and identify potentially promising methods to undermine these services by increasing their costs of operation.

The activities and side effects of 5-lipoxygenase (5-LO) inhibitors can be predicted by identifying their redox mechanisms. In this study, we developed a fluorescence-based method to measure the redox potential of 5-LO inhibitors and compared it to the conventional, absorbance-based method. After the pseudo-peroxidase reaction, the amount of remaining lipid peroxide was quantified using the H2DCFDA (2′,7′-dichlorodihydrofluorescein diacetate) fluorescence dye. Our method showed large signal windows and provided comparable redox potential values. Importantly, the redox mechanisms of known inhibitors were accurately measured with the fluorescence assay, whereas the conventional, absorbance-based method showed contradictory results. Our findings suggest that our developed method is a better alternative for classifying the redox potential of 5-LO inhibitors, and the fluorescence assay can be effectively used to study the mechanisms of action that are related to redox cycling.

Advance fee fraud scams, also known as Nigerian scams have evolved from simple untargeted email messages to more sophisticated scams targeted at users of classifieds, dating and other websites. Even though such scams are observed frequently, the community’s understanding of targeted Nigerian scam is limited since the scammers operate “underground”. In this paper, we focus on fake payment scams targeting users on Craigslist. To better understand this type of scam and associated scammers, we built an automated data collection system. The system relied on what we term magnetic honeypot advertisements. These are advertisements that are designed to attract scammers but repel legitimate users – similar to how a magnet attracts one side of a magnet but repels the other. Using advertisements of this type, we offered goods for sale on Craigslist, gathered scam emails and interacted with scammers. We use this measurement platform to gather three months of data and perform an in-depth analysis. Our analysis provides us with a better understanding of scammers’ action patterns, automation tools, scammers’ email account usage and distribution of scammers’ geolocation. From our analysis of this dataset, we find that around 10 groups of scammers were responsible for nearly half of the over 13,000 total scam attempts we received. These groups use shipping address and phone numbers in both Nigeria and the U.S. We also identify potential methods of deterring these targeted scams based on patterns in the scammer’s messages and usage of email accounts that might enable improved filter of their initial messages by content and email address.

A silicon nanowire one-dimensional thermoelectric device is presented as a solution to enhance thermoelectric performance. A top-down process is adopted for the definition of 50 nm silicon nanowires (SiNWs) and the fabrication of the nano-structured thermoelectric devices on silicon on insulator (SOl) wafer. To measure the Seebeck coefficients of 50 nm width n- and p-type SiNWs, a thermoelectric test structure, containing SiNWs, micro-heaters and temperature sensors is fabricated. Doping concentration is 1.0 x 10(20) cm(-3) for both for n- and p-type SiNWs. To determine the temperature gradient, a temperature coefficient of resistance (TCR) analysis is done and the extracted TCR value is 1750-1800 PPM x K(-1). The measured Seebeck coefficients are -127.583 microV x K(-1) and 141.758 microV x K(-1) for n- and p-type SiNWs, respectively, at room temperature. Consequently, power factor values are 1.46 mW x m(-1) x K(-2) and 1.66 mW x m(-1) x K(-2) for n- and p-type SiNWs, respectively. Our results indicate that SiNWs based thermoelectric devices have a great potential for applications in future energy conversion systems.

We identified a novel class of aryl-substituted triazine compounds as potent non-nucleoside reverse transcriptase inhibitors (NNRTIs) during a high-throughput screening campaign that evaluated more than 200000 compounds for antihuman immunodeficiency virus (HIV) activity using a cell-based full replication assay. Herein, we disclose the optimization of the antiviral activity in a cell-based assay system leading to the discovery of compound 27, which possessed excellent potency against wild-type HIV-1 (EC50 = 0.2 nM) as well as viruses bearing Y181C and K103N resistance mutations in the reverse transcriptase gene. The X-ray crystal structure of compound 27 complexed with wild-type reverse transcriptase confirmed the mode of action of this novel class of NNRTIs. Introduction of a chloro functional group in the pyrazole moiety dramatically improved hERG and CYP inhibition profiles, yielding highly promising leads for further development.

Our objective was to determine whether lipocalin-2 (Lcn2) regulates cardiomyocyte apoptosis, the mechanisms involved, and the functional significance. Emerging evidence suggests that Lcn2 is a proinflammatory adipokine associated with insulin resistance and obesity-related complications, such as heart failure. Here, we used both primary neonatal rat cardiomyocytes and H9c2 cells and demonstrated for the first time that Lcn2 directly induced cardiomyocyte apoptosis, an important component of cardiac remodeling leading to heart failure. This was shown by detection of DNA fragmentation using TUNEL assay, phosphatidylserine exposure using flow cytometry to detect annexin V-positive cells, caspase-3 activity using enzymatic assay and immunofluorescence, and Western blotting for the detection of cleaved caspase-3. We also observed that Lcn2 caused translocation of the proapoptotic protein Bax to mitochondria and disruption of mitochondrial membrane potential. Using transient transfection of GFP-Bax, we confirmed that Lcn2 induced co-localization of Bax with MitoTracker(R) dye. Importantly, we used the fluorescent probe Phen Green SK to demonstrate an increase in intracellular iron in response to Lcn2, and depleting intracellular iron using an iron chelator prevented Lcn2-induced cardiomyocyte apoptosis. Administration of recombinant Lcn2 to mice for 14 days increased cardiomyocyte apoptosis as well as an acute inflammatory response with compensatory changes in cardiac functional parameters. In conclusion, Lcn2-induced cardiomyocyte apoptosis is of physiological significance and occurs via a mechanism involving elevated intracellular iron levels and Bax translocation., link_to_OA_fulltext

In this paper, n/p-type nickel-silicided Schottky diodes were fabricated by incorporating antimony atoms near the nickel silicide/Si junction interface and the electrical characteristics were studied through measurements and simulations. The effective Schottky barrier height (SBH) for electron, extracted from the thermionic emission model, drastically decreased from 0.68 to less than 0.1 eV while that for hole slightly increased from 0.43 to 0.53 eV. In order to identify the current conduction mechanisms, the experimental current-temperature-voltage characteristics for the n-type diode were fitted based on various models for transport of charge carrier in Schottky diodes. As the result, the large change in effective SBH for electron is ascribed to trap-assisted tunneling rather than barrier height inhomogeneity.

Tuberculosis is still a leading cause of death worldwide. The selection and spread of Mycobacterium tuberculosis multidrug-resistant (MDR-TB) and extensively drug-resistant strains (XDR-TB) is a severe public health problem. Recently, two different classes of chemical series, the benzothiazinones (BTZ) and the dinitrobenzamide (DNB) derivatives have been found to be highly active against M. tuberculosis, including XDR-TB strains. The target of BTZs is DprE1 protein which works in concert with DprE2 to form the heteromeric decaprenylphosphoryl-β-D-ribose 2′-epimerase, involved in Decaprenyl-Phospho-Arabinose (DPA) biosynthesis. Interestingly, it has been shown that the DNBs block the same pathway thus suggesting that both drugs could share the same target. Moreover, in Mycobacterium smegmatis the overexpression of the NfnB nitroreductase led to the inactivation of the BTZs by reduction of a critical nitro-group to an amino-group. In this work several spontaneous M. smegmatis mutants resistant to DNBs were isolated. Sixteen mutants, showing high levels of DNB resistance, exhibited a mutation in the Cys394 of DprE1. Using fluorescence titration and mass spectrometry it has been possible to monitor the binding between DprE1 and DNBs, achieving direct evidence that MSMEG_6382 is the cellular target of DNBs in mycobacteria. Additionally, M. smegmatis mutants having low levels of resistance to DNBs harbor various mutations in MSMEG_6503 gene encoding the transcriptional repressor of the nitroreductase NfnB. By LC/MS2 analysis it has been demonstrated that NfnB is responsible for DNB inactivation. Taken together, our data demonstrate that both DNB and BTZ drugs share common resistance mechanisms in M. smegmatis.

In mobile ad hoc network (MANET), each end-node operates as an end-host and as a router simultaneously. Thus differently from wired-network, the occurrence of network congestion in end-host leaves much room for consideration. In the case of MANET, we can improve TCP throughput by using flow control algorithm that operates between layers because that algorithm reduces packet drops which caused by network congestion in end-hosts (source or destination). In MANET, usually IEEE 802.11 MAC protocol is used in a link layer transmission of two neighbored nodes for reliability and hidden terminal problem. But this protocol does not offer flow control mechanism in link layer. Link layer flow control can prevent packet drops caused by buffer overflow that can occur just after packet transmission. And in result, this prevention of packet drop can reduce the waste of bandwidth and energy which are limited in wireless environment. In this paper, we propose two flow control algorithms called, respectively, vertical flow control and horizon flow control. We show improved TCP throughput and reduced power consumption in end-nodes through the use of proposed two flow control algorithms in performance evaluation.

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